I've only been playing this game since Friday (three days), but I've already completed 13 hours. This game is an addictive driving simulator, and an absolute joy to play.
As someone who has never really followed motor sports, and with a very minimal understanding of the tuning involved and required, I've been loving this game. I have pretty much avoided the tuning aspect of the game, but I have already taken part in 130 races. The technical side isn't my bag.
My biggest feeling is that this game is definitely a potential GT killer (can't comment on Forza, have never had an Xbox). The biggest obstacle to it truly being a GT killer is the minimal licensing (where's the VWs? The Buggatti? Let's call it Formula 1, shall we?) but that's mostly excusable at this point because: A) I am still exploring and learning the game, and B) it's hopefully just the first release in a brand new franchise, and of course C) the fact that Slightly Mad Studios is still apparently a bit of a minnow.
That being said, if it is indeed true that SMS is already brainstorming Project CARS 2, then the bigger studios and franchises need to catch a wake up. The incredible quality shown in Project CARS and the very obvious devotion to the details that matter from the team, shows what they are hopefully capable of in future releases.
The majority of my game time so far has been spent in the career mode. I'm chasing the "Zero to Hero" mode, and it's incredibly fun. I feel like there has definitely been a learning curve, and I'm not missing an XP and level up system yet. I know the hard core racing simulator fans would laugh at the aids I play with, but I feel that with time I'll be able to take my training wheels off. Project CARS is a surprisingly good teacher in the art of racing, purely through giving you the experience without tutorials. Of course, you need a basic understanding of driving and certain principles involved. I feel that if I had never played a racing sim before, I would have easily abandoned this game as too difficult, but that's part of why I like it.
The not so pretty side now. The game, after being delayed a few times, still lacks the polish you'd expect from something that came out 7 months after it's initial release date. One or two issues with settings re-setting themselves and "Simulating session" screens blocking race menus that I've experience shows that they didn't catch all the bugs in time like they were hoping. However, it should be noted that this is far from the fiasco that AC Unity was, and it's better than any FIFA before 15 in terms of glitches present. This was an ambitious project, and I've fully understanding of the very small things I've seen, especially since I've heard they're already working on fixes for those.
The visuals should be touched on, at least. This game is gorgeous. After playing hundreds of hours of GT5, which was a mixture of visual polish and blocky laziness, this game has yet to show me an ugly side (visually, in the actual racing part). I don't care what the spectators look like, or the interior of the garage. The scenery is amazing to the point of distraction (I've crashed several times from losing concentration) and the cars themselves are eye candy, enough so that I've been sorely tempted to drive in "third person" mode. An amazingly aesthetic game.
My verdict: I have found my favourite racing simulator ever. I'm sad some of the cars I want to drive aren't there, and that some of the tracks I want to race on aren't licensed, but I'm very satisfied with the experience I'm having. When a game gets me addicted to it within hours of buying it then it and its makers deserve a heap of credit. Three thumbs up.