I'm really disappointed in Gamespot's gaming ability. Here's the low-down on the whole difficulty thing.
The game itself is just great, the graphics are great, the driving is unbelievable (I prefer the static view because you can really know where your car is going, but the in-car view looks great), and Los Angeles is mapped amazingly. I have had no problem with difficulty though; sure if you run into an oncoming car going 100 mph you're going to spin-out but it all makes sense and there have been plenty of times where I have recovered and caught up to the opponents. When GS said that "it seems like the AI have unlimited NOS," I just couldn't believe it. You are able to draft your opponent for a bit and charge a "turbo boost" at no cost and your opponents can do the same (and you can see when they are doing it to you).
There are easy races, green, which are very easy, yellow, which are still pretty easy, orange, which are a bit difficult but certainly not impossible, and red, which are races against opponents that are obviously faster than you. As you upgrade your car (forgot to say that the upgrade system is very intuitive and I enjoy it much more than NFS:UG2), your hard opponents will become easier to beat. There are so many races to do that you shouldn't even have to race a red opponent if you don't want to. You can always race enough people to earn the money to purchase a new ride, upgrade your own, or get their ride.
The game is by no means hard, it's just a challenge, and if you are wanting to just breeze through and be able to beat EVERY single opponent with no difficulty then there would be no reason to play the game. The difficult is just right.
People who enjoy cars, racing, or racing games will love this game due to it's fun atmosphere and story line. Don't go by Gamespot saying it was impossible.
EDIT: Forgot to add my ONE issue that was very annoying. While driving, you will get random pop-ups of racers saying they want to race you which pop-up RIGHT over your GPS, and if you have a destination, you will be very annoyed by having to wait it out or press back to go to your map and then get back to the game in order to get rid of it. It seems very annoying. It may seem minor but if you are trying to get to a race and have it pop up you are left with no idea of where to go. Very bad positioning on their part.