For Unity, there is a new complete Car Tutorial and scripts
I don't have tried it, but it's looks lot more simple now to make a car with physics without programming, juts adjusting
some variables in the program !

Well a video of a boot camp for Unity 3.0 : promising
Unity 3.0 Bootcamp

Unity 3.0 is beocming an AAA engine, and for the price if you have a team, a great project, designs, it's a way to go indeed ! So mall price for the pro version and for such great technologys that will have 3.0 !

But for indies, and lonewolves, A7 (A8) remains a very good alternative, and some great commercial gales can be made with it, with some more work