The driving model seems to me to be a bit more responsive than Forza. The in car view is really good, and was my one big complaint about Forza.
The graphics are sharper than those in Forza, but this just seems to be a difference in philosophy. GT5P has a cleaner and more spartan look, while Forza plays up the naturalism and lighting. Having said that, the London track looks absolutely amazing in GT5P.
The review cameras in GT5P are outstanding, far better than anything on offer in Forza. But Forza has better car customization options. The front end menus are a lot nicer in GT5P though.
Online can be choppy if people have poor connections, but I've had fun so far.
I'll really have to buy a wheel to get the full enjoyment out of the game, I think.