Oh man, only played like an hour so far, but it's awesome. Like the very first tutorial mission, it's the same quality as your normal "AAA" rail shooters, but in addition to shit like that it's open world and has TONS of stuff to do. And the graphics look great - plus it's my first GTA on PC, so being able to actually aim properly is really nice.
And even though GTA claims I'm using 2200 MB of 2000 of video memory on very high settings, the game runs 100% smooth.