Anyone else been having a go at this?
Yeah, some weeks back. It wasn't very well received, with complaints not only about the graphics of the demo but also of the car's handling. However, over time the complaints about the physics seemed to die down, but the graphics complaints more or less remained. However, as is frequently pointed out, the demo is of very limited file size, so it could simply be that what people see in the demo isn't a good representation of how the final game will actually look.
Fortunately you can configure the controller settings however you like, since Polyphony went with a retarded scheme of using the D-pad for steering and the face buttons for throttle and brake. I quickly mapped these to the left analog stick, R2, and L2 respectively. I still wasn't able to enjoy it at all until I found me a decent controller, since reaching to the middle of the controller for the left stick is just plain retarded and awkward. A couple weeks back I finally got a decent controller for my PS3 (Dreamgear Shadow 6) and was able to play the demo properly.
I don't remember what kind of times I posted but I only ran a few laps originally with DualShock 3 and then a few more with the Dreamgear Shadow 6, which surely isn't enough practice to go for a competitive time.