Loving it so far, not sure if it will have the single player longevity of Forza 4 though, hopefully the Rally update will add some interesting time trials as I'm more of a hot-lap kinda guy.
All nicely put together, it seems to be throwing cars at me at an alarming rate (around 15 within 2hrs, without really doing much)
Only minor complaints so far is that it's nowhere near as good as TDU2 if you want to pretend to drive like real life for a bit (not enough traffic, no indicators, idiotic Horizon competitors that hardly even acknowledge your existence), and the "story", as expected, is appallingly put together.