Apart from being not a fully finished game, having trouble with wanky AI Drivers, Server Connections and so on it's quite a good racing simulator. And it is a Simulator, which needs some practice and consistence.
The amount of cars and tracks off-the-box isn't that high, but the quality of them is. Having a look at Spa for example, it's a great detailed and laser-scanned track, which is a sheer pleasure to drive at. Same thing with the stock driving vehicles - it's a reward if you learn to handle them.
Of course, there is no rain like in pCARS, no night or weather at all, not that much eye candy stuff in Assetto Corsa. Kunos SImulazioni focused on the driving and the physics of the vehicles and with that it delivers excellent force feedback on many supported wheels.
Probably the most outstanding thing is the modding community, as it's really active and gets sometimes even featured by KS, which is great. The driving community on the other side is like in almost every other game full of nerds, midskillers and ♥♥♥♥♥♥♥s alike. Don't expect the best experience, when you join a server with random people in it. ...oh and better wait at Spa and look how they manage to get the first corner after the start ;)
Seriously, it's fun and if you're into cars anyway, check it out! Thumbs up here!