The trailer is slickly done and a joy to watch as a trailer. Though I guess I should be thinking how the gameplay is, I seem to be a sucker for some editing, pacing, and a little punchy music.
Speaking of the gameplay, DMA (well Rockstar North or whatever they're called now) seems to be really pushing more realism with this proper sequel. From what I read from the previews, cars take time to steal, guns are bought discretely from the boot of a car, and Nico's cellphone plays a heavy role communicating with bosses and luring targets. However, all that nifty stuff won't mean much to me if it isn't easy to shoot and kill. I never did like how combat felt in GTA3. Always I thought, "oh god, just give me a proper and simple dual analog set up". That's something that made Mercenaries: Playground of Destruction a joy to play (that, and airstrikes).
It seems that there are alot more indoor places than I remembered being in GTA3. I think that is a very nice thing for the series. Hopefully, there will be more sticking and deep consequences, whether they are strictly plot triggered or a bit more spontaneous. From my experiences with the series, it bothered me that you didn't have much of an effect on the world and vice versa. Then again, I can't really think of what I'm after by saying that.
As for the framerate, I never dwelled on its obvious choppiness when watching the trailer. Damn, I got to engossed to the music and dialogue.