Let me get straight to it. This game is fun. Fun to the point of insanity. I thought the AI in Mario Kart was bad at not letting me get to far. The AI in later levels of this game are brutal. Combine that with sense of speed and I just couldn't get into this game. Sure I like challenges but something about this game just turned me off.
One thing I've never been too keen on is the fact that you have to try over and over and if you miss anything by a hair, you have to try again. Pinpoint accuracy has never been my forte. Sure I can snipe quite well in shooters but I've never been able to do it under pressure. This game pressures you to the point that you can't make a single mistake.
Games that demand perfection are not considered fun to me. I like to mess around, experiment, and try new things. Sure it doesn't always work out but I can say that experimenting in this game is a good way to lose.
I will say that this is one of the few games I've ever played online with friends. This is the one thing I rather liked. The online is quite smooth and having a whole room full of people you know is fun. Sure there are people that will ruin the fun by being incredibly good at the game but there is enough random chance that there is just a slim set of hope that you could win to keep it interesting.
I still prefer Mario Kart to this series but I think I would buy another one if I see it for the right price.