Well, I saw Transformers: Revenge of the Fallen, loved it, and would go watch it a second time.
Yup, it was that good. But just a few things you need to note if you haven't been to see it and are on the fence. I recommend it, for sure. :)
Here's what you need to know:
1. It's not Oscar material stuff, so leave your brain at the door and enjoy the ride. :)
2. When you're waching, don't go: "What? That wasn't in the original cartoon! It's all crap they made up!" Well, I can tell you for sure that there was a lot in the original Transformers mythology and history that was never in the 80s cartoon. It would've been too complicated for kids. It's all in the movie and all true, though. A visit to TFwiki.net will set you straight. It did for me. ;)
3. Enjoy the action, but listen to the dialogue! There's a lot to see in the movie but don't let that distract you from the witty one-liners and the excellent voice acting. I know it's tough to discern who's saying what when one robot is bashing/tearing/blowing apart another. But if you can do this, you'll find the movie makes good sense.
And finally, for those who've already seen Revenge of the Fallen, here's a little of what happens when Sideswipe is telling Henkei (G1) Optimus Prime about his part in the movie, and a shortchanged and disgruntled Sideways overhears them. So SPOILERS ahead. Enjoy!