Buggy but otherwise good
For starters, the subtitles are dyslexic and full of grammatical errors. My teenage kids can spell better than that. For instance, something is better "than" something else, not "then".
Secondly, and possibly the most annoying part of the game (and the one that kills all replay ambitions) are the annoying cut scenes that can't be skipped. I've played the run through three times, and watching those clips is about as exciting as watching grass grow. Right in the beginning after the first race, you have a good five minutes of animation which requires no user input and has no bearing on the game. Why couldn't they have a "skip" button there?
Thirdly, affecting multi player mostly, the game has a tendency to crash when it loses Internet connectivity. It starts when it tries to retrieve the race in the first place. There seems to be no mechanism to prevent the game from waiting for a race for eternity. At one point, my console was sitting there for a good 15 minutes claiming to be connecting to the Autolog servers. Worst is when you are in the middle of a race and the net drops out. In those cases, the game just stops there and then - at times even locking up the console.
Other than that, the game is awesome. Funfactor is great, the Challenges are actually challenging. The cops are heaps of fun (except the annoying head on pirates) and you can spend many a day or night racing.
The Single Player campaign is pretty much the right length and the races and cars are awesome.
The Multiplayer campaign is not as strict on the physics but is heaps of fun and the added multiplayer challenges give you a good incentive to play it again and again.
I especially like the fact that you can increase your ability level both in Single and Multiplayer which means that if you are stuck in the run you can actually increase your abilities by playing multiplayer and are not doomed to play the same levels over and over as in previous incarnations of the NFS series.