I've played for years and it is absolutely the best racing simulation out there.
Well optimized, I've never suffered any stutter or lag whatsoever.
Graphics may not be absolutely cutting edge by todays standards, but there is certainly not anything lacking in the visual department. ( The actual game looks much better than the promo videos, believe me ) I do find that user made skins available at mod sites generally look superior to the stock car skins.
Cars have excellent physics and feel, controller set-up is easily customized to suit your style of controller and play, car setups can be finely tuned with many many variables which accurately mirror real-world tuneability. Alternately, pre-configured set-ups are available online.
There are a huge number of different cars and tracks to suit any skill level or particular interest, Everything from high-downforce open-wheel racing, to touring cars, minis, etc etc. I prefer the vintage sports cars myself, the Retro pack with GT Legends mod brings me back to the golden years of vintage sports car racing.
The modding community is still very active, there are too many user made cars, tracks, skins, and effects mods to list, which add a lot to the game, and are not very difficult to install and run.
In summary, if you are a racing enthusiast and you don't have this game, you are really missing the boat. Don't expect any "yo dude, that was so gnarly" as in, say, DIRT2. What you are getting here is pure racing, and nothing but. At this price, you're stealing it. So get it, and drive it like you stole it.
Is it easy? No. Are you going to jump right into the most powerful car and dominate the competition? No. This is not an arcade game, it's a simulation. There is a learning curve. You may learn that you actually suck, at first anyways. Ever watch racing on television and think; "hey I could do that no problem"? Here's your chance.
Think you're fast? Find out.