First the movie. It's edited pretty well, and it certainly doesn't feel like it's over 3.5 hours, so it doesn't drag. The extra narration (which isn't much, really) complements the story well. The quality isn't as good as the in-game cinemas, though, due to space, I'm sure. But the quality of the MGS4 trailer is amazing. If you want any specifics on the movie, I'm happy to answer.
The 3D camera makes a huge difference, I never use the old overhead camera anymore. It works exactly like the Splinter Cell camera, if you're wondering.
The old MG games are faithfully recreated. I've played both in emulation, but being able to use the PS controller and an easy save/load system is much nicer.
There are 2 new Secret Theater movies, one with The End that is really funny. The Snake Eraser movie is also hilarious.

A lot of the extras in the game were included in the European version, but if you have a completed save from the original game, these are all opened up at the start -- the Demo Theater (including the Pink Roll), Secret Theater, Duel Mode, the extra Snake vs. Monkey levels, the Briefing, and the Camo Download.
From what I can tell, choosing "I like MGS3!" at the start gives you new camos. And all the camos, including some new ones, that were for download online can be downloaded straight from the game to your memory card after completing the game (or if you have previous completed data from MGS3), but they still take up way too much space. I'm sure that was done to discourage people from having so many at once.
All in all, amazing package. And that's not even counting the Online Mode!