I'm going to avoid spoilers to the extent I can, but I don't think it's much of a spoiler to say that Abrams does something a tiny bit like the Crisis on Infinite Earths—i.e., he comes up with an in-universe reason to break and more cleanly remold canon—although his explanation is more traditionally Star Trek-like, and the result is more like a reboot than a simple cleanup.
In fact, comic books aren't a bad model for the most compelling, cinematic stories in Star Trek. They share a lot of the same elements: a heroic group of people with fantastic (by today's standards) abilities must face an even more powerful set of villains. (There are four other kinds of episodes—the spatial/temporal anomaly, the moral dilemma, the tech malfunction, and the character episode—but these don't really make good movies.) And that structure creates the same problem seen in comics: you always need a nastier villain next time, so the heroes and villains end up in a sort of arms race.
We see this sort of problem in nearly every long-running franchise, though some of them suffer less from it than others. James Bond doesn't face a more difficult villain in every movie, and that doesn't bother people. (The gadgets are another story, which I think is why they were omitted from the reboot.) Nobody complains when Bond takes down a world-domination-oriented organization in one movie and then a gold thief in the next. On the other end of the spectrum, Dragonball and its derivatives are notorious for this.
This Dragonballification of Star Trek has become increasingly obvious. Consider writing a post-DS9 story: the Federation has already pounded an empire spanning a quarter of the galaxy into submission and phasered another major enemy back to its Stone Age; what do you do now? It becomes even worse when you add in Voyager: equipped in the finale with the sort of arms that an eleven-year-old fanboy would come up with (I should know, I still have files from when I was eleven), one ship singlehandedly toppled the nastiest regime in the galaxy.
What sort of enemy could possibly still take on the Federation? Nemesis used a bunch of tricks to get around this, from political intrigue to blatant fanboy bribery ("Ramming speed!"), and it still couldn't save its box office numbers. And it still pretty much completely ignored the Voyager finale's godmodding technology. (I enjoyed Nemesis, but it wasn't as good as, say, First Contact.) They can't do this forever.
This is why Enterprise was a prequel series: unable to go forward, they had to go back. And yet, still run by the same folks who screwed things up so badly with the ends of DS9 and Voyager, it then proceeded to make the exact same mistakes, skirting the edges of canon all the way.
Hence the reboot. It returns us to an earlier time, when the Klingons and Romulans (and apparently Cardassians—they were mentioned briefly) were at par with the Federation and still hostile. Its timing gives a reason to turn TOS's flat but colorful characters into more three-dimensional but still colorful characters. And its canon-breaking changes the universe so that it's less susceptible to the escalation trap.
I loved the old canon, but it needed to die for the franchise to live. And Abrams makes that happen.
And it doesn't hurt that the rest of the movie was so well executed. The ship was a combination of the original show's stark look, lots of dynamic futuristic blinkenlights, and enough buttons and switches and hinges and axles to make it seem like a real, physical piece of technology. The phaser effects were fresh and exciting and real in a way that Star Trek's hand weapons never have been. Even the uniforms were gorgeous—they look very much like TOS's, but they have a pattern and texture to them that makes them look crisp and official instead of cheap and campy.
The plot was great. The casting was spot-on and the characters were very much like everyone remembers, only fleshed out in the way the first six movies tried to do but never quite pulled off. The villain was all around well-designed. (I won't talk much about these to avoid spoiling.)
And Abrams took great pains to reassure fans that he's thinking of them: Trekkies got a shout-out every ten minutes. Some of them were things almost anyone would catch (even my brother, who isn't a big Trek fan, noticed the red shirt was the first to die); others were subtle (Pike being in a wheelchair); still others were downright obscure (I was the only one of the three Trekkies in my family who caught Scotty's Enterprise reference). There were probably ones I didn't even catch, and when I notice them the next time I see it, I'll be delighted again. Like giving a kid a lollipop after a vaccination, things like this helped fans feel better about the bold move Abrams was making.
And it worked. I haven't enjoyed a movie so much in years—and I have never been as big a fan of Kirk, Spock, McCoy, and Scotty (not to mention Uhura and Sulu—wow!) as I am right now. And all while leaving a new, sustainable base for the series to build on. Well done, Mr. Abrams; I hope you stick around for the sequel.