Porsche Unleashed was my favorite in the NFS series. What I liked about it was racing on open roads with civilian traffic. In the demo, there is one closed circuit track, with no civilian traffic, and one long open road, with no civilian traffic. I thought the closed circuit race was really weak, and the open road speed trap race was pretty good (but wish there were cars to dodge).
It isn't 1 crash = death unless your crash is super bad. 170mph into a wall = death. 100mph into tree = lose your hood. I think that is fairly balanced.
I've been playing Forza 2 on Xbox 360, and though it is pure sim, I think it is much much more fun. Without the things that made NFS unique (chases, police, traffic), I don't think it stands up well to the other driving games out or coming out soon. Demo may not be representative of the breadth of final game, so we'll see.