This game most certainly gets a lot of hate, but I feel personally like this is a worthy title for racing fans. However...
This game doesn't run very well AT ALL on lower-end gaming PCs. If you want a Trackmania game and you don't have a great PC, stick with Nations Forever.
Off-roading is much more difficult in this game in comparison to its counterparts. Using a controller rather than arrowkeys is strongly recommended for this particular game.
I have seen Trackmania getting a lot of hate from parents because their kid didn't like it. Trackmania is not the kind of game to just pick up for your kid. This game especially is very difficult at times and can lead to frustrated outbursts. Generally best for very experienced racing gamers or people who don't take anything too seriously.
Many parts of this particular installment seem unrefined and slightly sloppily assembled. Sound and music tend to cut out a lot especially. Custom-made tracks don't seem to have this problem quite as badly, but I would still recommend listening to music from another source while playing this game.
Overall, however, I would say this is a good game. Controls are basic and the gameplay is straightforward. The Vally setting is gorgeous and the track editor is fun to mess around with. Physics are closer to those of Canyon, except with looser steering and slightly more difficult drifting. Takes time to get use to the unique phsysics of this game, especially on the off-road parts, but you will eventually get the hang of it.