I've bought this game recently, which is 2 years after it first came out. The visual is still great for a game nowadays. The sound in the game feels quite satisfactory when skidding along corners or accelerating in full speed.
In single player, I especially liked the feeling of accomplishment I get when I finish 1st in a race because you have to be constantly focused every time you turn around corners otherwise you will easily end up 5th from 1st. And there are a number of disciplines to master ( Touring Cars, Open Wheel, Drift GP, Formula 3, etc ) so it can be a challenging but satisfying journey to winning all the events to get to the first rank in the game.
There is a wide range of difficulty setting also and it's a great feeling increasing the difficulty level as you become more and more proficient at driving.
I haven't tried multiplayer very much but there are still enough people playing every time I go online.
This game should be an excellent training wheel for newcomers waiting for GT5 to come out.