The movie didn't go backward on itself - Vulcan is destroyed, Spock's mother Amanda is lost, and there's no going back to save either. Kirk's father was lost 25 years before Kirk became Captain of the Enterprise - there was nothing that could have been done short of time traveling and creating an alternate reality which is the result of time travel most-supported by scientists today, if even time travel is possible, besides in the past (though time is relative, if you go really fast and go forward in time faster, everyone else is sort of going back in time, relatively speaking, proving that time travel is in fact possible, at least to some degree). But the point is, this movie wasn't like all the others. There was no B4 to provide continuity to his late brother Data. There was no 'katra' or 'holy spirit' that would revive all 6 billion killed on Vulcan. Spock just wasn't fast enough to save his mother, and there was no going back on that.
The movie was highly tragic in these ways, and awfully sad I must admit. I had tears the first time seeing some of the scenes - mostly with the sacrifice of George Kirk, the loss of Spock's mother, the destruction of Vulcan, and the father-son talk between Sarek and Spock on the transporter pad after Kirk took command of the ship. These are the things that absorb me in the movie - during most of the movie, I didn't feel as much like I was watching a movie, but a lot like I was in the action as an observer within the same reality. And for me, it takes a darn good movie to do that!
However, no movie is really devoid of problems, and this one is unfortunately not an exception.
The whole "Romulan star supernova threatening the galaxy so we have to use two ounces of red matter to somehow create a black hole that's massive enough to pull in the material from the supernova, although as the black hole's forming it initially has very little pull as the shockwave and material of the supernova fly by at horrendous speeds" thing was simply so far-fetched that even Spock's katra sounded realistic in comparison.
So, the Romulans are an off-shoot of the Vulcans. In fact, they're the same species, only that Romulans evolved differently having lived on Romulus. But the split occurred when some Vulcans decided to "reserve" their emotions while others decided to say "well, frak that!" and headed off to Romulus.......3,000 something years ago, somewhere around then.
This implies in the first place that the Vulcans had great technology long long, long before humans ever did - not just decades or centuries, but even before the birth of Christ!
So both Vulcans and Romulans should be far more than a match for humans. Depending on when the Borg evolved to create their technologies, the Vulcans and Romulans might be said to have evolved their technologies far before, which in logic would mean that the Vulcans and Romulans could literally wipe the galaxy of the Borg with little effort - that isn't the case though.
But logic falls apart even further in Spock's description of the Romulan star going supernova. The Romulan star could be assumed to be much like our sun. I mean, it may have the essential 2.8 times the mass of our sun to go supernova, but it couldn't be much more than that, making the threat of a supernova to the galaxy a very far-fetched and completely unrealized type of logic.
Also, if the Romulan star was to go supernova, it is likely that the star we saw in "Nemesis" which looked much like our sun would have instead been a red supergiant by the point it lost radiance and lost the fight to gravity that would cause a supernova explosion.
But let's consider that our science is way off right now, in 2009. Let's consider that a supernova could possibly threaten part of the galaxy or even the entire galaxy...that wouldn't make sense. Many stars went supernova before our sun was formed - and it was for this reason that we have many of the heavier elements on Earth - elements that are essential for planets to be made of the stuff they are, and for life.
Obviously, supernovas were never really much of a threat to an entire galaxy - we can see this in observation today. The most you could get out of the collapse of an extremely massive star is a possible gamma ray burst, a black hole forming, and perhaps the "disruption" of star systems within 500 light years. Obviously, if you're hit by a gamma ray burst from a star that went supernova in your own galaxy, half your planet is toast in tenths of a second. But that's not normally the case. There is little evidence that the Earth was ever hit by a gamma ray burst in its entire 4.6 billion years. It seems highly unlikely that in its last 2 or 3 billion years that it will ever happen either. This Earth will probably only support life for up to 800 million years after this point, because of the shutting down of the necessary tectonic plate engine that renews the Earth, along with other likely problems to be faced (the moon possibly escaping the Earth system).
So anyway, Spock shoots a small amount of Red Matter at the approaching wave. And...it starts sucking up massive quantities of the wave. But given his close perimeter to Romulus, that planet would have been eaten up too, even if the shockwave from the supernova never reached Romulus.
Plus, you have to consider that he shot this red matter at one side of the supernova. It's rather unlikely that the black hole would suck up the WHOLE supernova. Spock's efforts would have failed either way.
Also, it is to be assumed, logically, that if a star were showing signs that it was going to collapse anytime within the next million years, those living in old Spock's time (which is in 2387 according to one misquote of the movie that states his ship was commissioned on Stardate 2387, not the year 2387 which would be the correct assumption since he is from 120 years in the future) would know about the star going supernova by this time. Evacuation efforts would have been long passed by the Romulan government and no harm would have been done at all.
But they'd even have warning if the star began swelling due to the lack of hydrogen and helium that would cause a star to begin losing its war against gravity. In 2379, when Nemesis takes place, there seems to be very little (visual) indication that the Romulan star was even close to the end of its life. If there had been, Romulus would have been devoid of life by this time, because it is within the habitable region of the star's influence, and would be either devoid of life when the star destroyed the planet as it expanded, or would have been molten by this point. Both situations would kill all life on the planet with relative ease.
So...this was all a way to create an evil villain...Nero. Spock pretty much did cause Nero to capture Spock's ship so that he could use it to destroy Vulcan. And the black hole device red matter thing had to have some sort of origin. It's just too bad this part of the plot seemed to be slapped together in the last minute.
Kirk finding Spock on the same planet, in the same location...probably as likely as aliens landing in your front yard at 3:33 AM tomorrow and presenting you with a rose, and then vaporizing you immediately after their gesture of assumed peace. It is about as likely as going on the corner of Main and First street and finding the winning lottery ticket, and then going to that same street corner at the same time the next day and finding the winning lottery ticket in the same place, and having this happen everyday for the next 1,000 years!
Also, Delta Vega is a sister world to Vulcan? Well, you learn something everyday!
Last thing that seems to have a lack of making sense...Nero somehow needed to use a laser drill to get to the core of Vulcan so that he could put the red matter in the core. Well, if Spock's experience was any lesson about how impossible red matter creating a massive enough black hole to suck up a large amount of material, Nero could have just fired the red matter at the surface of Vulcan, and armed some torpedoes to ignite it. The effects would have been similar.
Now onto the less obvious fractures in mechanical and quantum physics...
Nero and Nero's ship...a bunch of bald Romulans with the exception of one, who had hair. And everything about Nero's ship has "Scimitar" written all over it! Obviously, from the late 2370's to the late 2380's, the galaxy has had a lot of problems with Romulus and Remus - they make the Borg look like common thieves by now!
Nero's ship may as well have a bunch of Reman troops on it, because it was almost like dejavu anytime that ship or the troops aboard were shown on screen.
Also, just about everyone on the bridge crew of the Enterprise was far younger than the rest of the crew of the ship - sort of a reversal of what is most common. The average age of the bridge crew had to be around 22. That...is some weird stuff.
And then there's the thing with Spock and Uhura. I'd have to assume that in the normal timeline or reality, they never hooked up. So somehow, Spock's older self from the regular timeline interfering with matters created a situation in which his younger self was in a relationship with Uhura, Kirk becomes Captain...of the first ship he's commissioned to, and for some reason the Enterprise bridge has some weird vertical tactical thing like you'd see on a submarine, or on the Empire Strikes Back alliance on Hoth base thing. Neat.
It was difficult to see how Kirk and Spock were ever in any real danger - I never really got that sense from them. It was almost as if they were in a simulation and not a real life and death scenario because of how seemingly casual they were. When a planet with 6 billion on it are killed, and that planet had most everything to do with the founding of the Federation itself, I would expect everyone to immediately and all at once pass out or require a bath or a change of undergarments.