Not a simulation, not an arcade, maybe a perfect mix!
Lets clear something from the start, Grid is not a simulation. The developers themselves have it stated, unequivocally. The difficulty settings available can turn the game from a pure arcade to a more sophisticated experience (Grand Turismo comes to mind, well almost) where you need a wheel and pedals (as in a simulator).
The game offers a nice "career" mode, except the usual instant race option. As you progress and win races, you sign sponsors, you earn money, you buy better cars and so on.
The cars available are numerous (43) but not whole classes as someone expect. What that means? An Example : You can drive Touring Cars but only the Lacetti and the BMW 320. Same applies in GT3/GT2 but in GT1 and prototype, things are better. Also drift and muscle cars are available, completing the satisfying experience!
I like to mention the option (difficulty setting) of gameplay, to rewind time (10 seconds), something very interesting for the casual gamer, i believe, as saves from frustration on times when in the last corner, the bugger in front of you, turn in its length. :D
I've played the game both with a gamepad and a wheel. The gamepad is not precise, making the driving in higher difficulties impossible. With the wheel the game is a pleasure and the multiplayer matches are very fun and satisfactory! Speaking about that, multiplayer is one of the best parts of Grid. Its fan, fast and highly competitive.
So ... worth every euro! A highly addictive and fun game which will accompany you for days, maybe until Codemaster's, F1 2010 arrives!