I am somewhat obsessed with this game after having it for a couple of months. It is incredibly good. Best driving/racing game I have ever played.
Certainly difficult -- way more so than '10 and '11. I like it, adds to the realism. The way an F1 game should be, imo.
Took me quite a while to work up to "Legend" difficulty level. Still I can't qualify better than mid teens on certain tracks.
Also really like the emphasis on setup. Aero, brakes, engine mapping, gearing, all really impacts performance. And yes, seems they want you to figure out the right setup.
My complaint is the AI is questionable in some circumstances. Way more interference from slow going cars in practice and quali than is realistic.
Only other downside is that it has made Forza a snore! I find it basically unplayable after F1.