Pretty hard at first, but once you get used to the levels and controls, this is one hell of a game.
The gameplay is VERY fun once you get used to it, especially the multiplayer. The story mode is hard, because in most levels, you will have to finish first, but it will also keep you entertained.The mission mode is very hard too, because you have to get everything in a level to get a gold emblem. Get a gold emblem on all missions (I think near 100) to unlock Super Sonic. Get used to pressing START and restarting the race/mission. The only problem is that your opponents are very hard to beat and you run out of boost to fast and then you are forced to walk on foot.
The graphics are very nice, except I was hoping the cutscenes would be more like the ones in Sonic Heroes.
The sound of the levels are very nice, mostly techno. Omochao is the annoying announcer. Also, I thought Jet would talk cool, but I was sadly dissappointed. Anyway, it isn't that bad for the most part.
There are plenty of unlockables and boards, trust me, you be playing this game for a long time.
This game is worth buying, I am so glad I got this game.