My initially positive reaction to seeing the game running was quickly tempered by actually getting my mitts on the iPad re-release. Which is to say, "The moment I stepped out a car, the game became frustratingly difficult to control." Those of you who played the original game (so ... uh ... everyone) will remember that, even on a DualShock 2, GTA3's strong suit was never wielding Claude as a rogue gunman, but rather as an automotive madman. In simpler terms: it was far easier, and far more fun, to drive around in a car than to be on foot.
The same applies to the iPad iteration, which has context-dependent virtual buttons overlaid onto the screen in the botton left and right corners for each of your corresponding thumbs. In my experience, this made driving bearable (but not by any means elegant), and the inevitable cop chases were damn near impossible. The few times I was forced out of a car (usually because it had flipped), defending myself became a measure of getting to another car rather than firing back, as the virtual buttons weren't very helpful when multiple police officers were firing rapidly on me.
Like Duke Nukem 3D on iOS and many others, GTA3 seems to suffer from the problem of never having been intended for a giant touchpad screen, and therefore doesn't translate well to the iPad -- at least the build I played, a month or so away from launch. But if Rockstar follows standard App Store pricing models and puts the game at a low price, it'll be a fun novelty for many with a low barrier to entry. And maybe that's all that it needs to be.