See it in IMAX 3D.
No really. The 3D is astoundingly well-done, and the bass in IMAX theaters is so loud and deep that every time a Kaiju takes a step, you'll feel like it just thumped down next to you. Holy crap does the IMAX experience rock for this.
I saw this twice already. (Prescreening and yesterday after release in Boston.) I predict a lot of people will complain that even though it's already a 2.25-hour movie, it doesn't have enough slowed-down character moments and there wasn't enough focus on the Drifting between the two main characters and that two of the Jaegers died the first time they were sent out and thus we didn't get to see them fight more, just the main two that were needed for the Big Final Mission.
The problem is, if you added anything to this movie, it would turn into a Lord of the Rings-length monstrosity. Del Toro couldn't have fit anything else in here, or it would have padded out the movie. The point isn't for this to be a big dramatic character movie; the point is to show people characters that they already understand, in an interesting way, so that they can get straight into the world as it is and follow along as we see this incredibly small snapshot of what's going on. The movie represents the last dregs of the Kaiju war, not the whole shebang. It needs a very quick and brusque setup just to get off the ground, and we can't waste time faffing about with the main characters' issues. We know they have them; we can assume they're putting them aside because IT'S THE END OF THE WORLD, WHAT ELSE ARE YOU GOING TO DO. If you can't manage to deal with your psychology in the face of THE END OF THE WORLD, you have no business piloting a giant robot in the fight to keep said end of the world from happening. Presumably this is why the character development goes so quickly -- you don't have *time* in this setting to go through a huge character arc. It's one shot, one try, no retries. You screw up, and the world is over. How many times have you yelled at characters for not sucking it up in the face of epic consequences? Probably a lot. And finally when they do so, you don't really get to complain, because it just makes sense.
I liked that. It made things simple but not stupid, as Bob said. Giant monster, punch it in the face. There's no time to freak out when you're about to get ripped apart.
The main problem I see with the movie, which isn't big at all to me, is that the worldbuilding was a little weird, in that the entire human race got hit by Stupid Rays at the beginning and every government has decided that the Jaeger program is lame and let's just build a giant wall instead. Chuck "Egotistical Jerk with Daddy Issues" was right -- shitty pilots were probably what was dooming the program, because when decent pilots went out there against bigger-than-usual kaiju, they mostly still won. But this is really the worst part of the movie, and I can live with a bit of inconsistency just to see the rest of the awesome.