Short verdict on the driving physics:
1) The cars are much grippier, but then I always thought the GTA4 ones were a tad too slidy. Now they're a tad too grippy, but still fun to drive.
2) Crashes are way worse than in GTA IV. I guess they got rid of the soft body eformation of GTA IV for performance reasons, but due the almost complete lack of deforming (instead, parts fall off), the crashes feel like bumping matchbox cars. Also, there seems to be an issue with car weight. When hitting a car of the same or a higher weight, your own car seems to skid around it upon impact, with little to no impact on the car you hit.
Also, I got mostly two results from crashes: either the "skidding" around the obstacle with no real loss of traction or orientation, OR it's flipping all over the place with multiple revolutions around all three axis', but nothing in between.
Still, a great game. But after about 5 hours in I still think The Last of Us is the best PS3 game of this year, if not of all time, even though I do like Sandbox games and dislike survival horror...