I don't care for the way that Rally is implemented in this game. It felt more realistic in the previous 2 games.
Dirt/gravel feels very "wrong" in this game. It seems to either slow you down more if you're driving slowly/steadily or it's like driving on glass all within a couple mph or so of speed difference. I used to drive on roads like these. Crappy country roads that were not well-maintained that were actually worse that what the ones in the game should be, in a crappy old delivery van. Hills, curves, and even potholes. I could take corners in that much quicker than I can in the game. The cars in the game are designed to handle these tracks. It should be better than it is.
The snow/ice ones are done even more poorly. It doesn't feel like snow or ice. It barely seems like a damp road. I dunno what they were trying for, but the Gold times are very very very easy to not only match, but beat by a mile. . . on a first attempt.
I was very disappointed with the Rally stuff. I had a lot of fun with them in the past games, but they did a lousy job of it for GT5.