Picked this up today. I think played for about 5 hours before I finally put it down. It's quite awesome.
This is the first game I have played, console or PC, where it feels like a open wheel car.
Forza 3 comparisons are inevitable, so here is my take:
Mechanics/Controls: Both about a 9. In Forza, if the car class and speed allow it, you can easily place a car within a millimeter of where you want. In F1, the twitcheness and a never slow speed make precise movements extremely difficult. Both controls have a similar default button layout.
General Driving impressions: I give F1 a 9, and Forza 3 an 8.
In F1 2010, you feel an instant sense of communication between you and the game. If a mistake happens, there is little to blame it on. It feels so connected. In Forza 3, this is mostly true with a few exceptions. Some of the fictional tracks are weird, more on this in second. And the sensation of speed seems way off.
Tracks Variety: F1 2010 a 7, Forza 3 an 8. F1 is holding true to the season and realism. No fictional tracks, all painstakingly recreated. But since it's only sticking to one season, no variety. No past tracks, like Indy, Magny Cours, Jerez, San Marino, etc. And no old Hockenheim, or old Spa, just the new ones.
Forza 3 has quite a bit, with variations for each. Included are old circuits from historical and fictional tracks. For example they have LeMans pre-chicane. And they have a new and old version for the fictional New York track (fictional venue, correctly modeled streets and buildings). Now the fictional tracks are really bad in Forza 3. Most feel disconnected. Nobody thought of simple momentum transfer in a few of them. Especially that awful Sedona course. And an improbable location for a racetrack as well.
Graphics: Edge to F1 with a 9, Forza 3 with a 7. Forza 3 is showing some age. The cars are awesome. But stuff here and there aren't that great. Mountainsides take simple polygonal shapes and look distracting. It's so bad sometimes. Also some decals are blurred out, like if the image file was sized incorrectly. Lighting effects are much better in F1, really subtle and realistic. Each car is modeled and skinned with multiple textures. Too bad they are too fast to appreciate them entirely.
However, Forza 3 maintains a healthy 60fps I believe, so it's always smooth. F1 not so much, it can stutter a bit.
Realism: Undecided. There are tons going for each, and the same old nagging things that keep holding down from me ever calling these sims. But, these games get better and better every year.
Presentation: Both are a 9. I love the layouts and graphics in both. I love F1's British minimalism in graphic design and typography. It goes in line with F1's ultra clean paddock and garage facilities. I also love the Magazine cover or Poster style artwork for each event it Forza 3. Really thought out, and really nice touch.
Replay: Still up in the air. I would say both a 9. Forza 3 has a huge long career, plus you can switch it up and try different ways to a faster car. F1 is just a regular F1 season at a time. But they try to make up for it by recreating the career drama of a real time Grand Prix driver. So you have to deal with the agents, contracts, the press, etc. Not very in-depth, but it's the right amount balancing immersion and and avoiding routine annoyances that might plague it if that was more in depth.