It's super hard! If you're worried about them making it even easier than Mario Kart DS (which was quite easy) they've gone the opposite and made it so that you can be in first on the final stretch, then get blue shelled, red shelled three times, then get run over by a big character, run over by a bullet bill, run over by someone with a star, green shelled then knocked about by everyone else then finish 12th. It's relentlessly hard on 150cc, I haven't finished it yet because it makes me silently scream and want to throw the controller into the console. You'd think that if you're at the back, you can easily claw back to the top. It's not always the case, because more often than not, the other racers at the back have all the superior power-ups and smack you around with accurate bullet bills and stars.
The online is a lot of fun if you're playing with friends.. because it just is a buzz seeing their name and their kart choice racing around with you. If you're playing with strangers it's just like the offline, it's totally random if you actually win or lose and you can be 12th and get lucky in the last 10 seconds and get 2nd or be 2nd during the last corner then get smashed into 10th. At least it's still someowhat fairer than the single player experience, although I've heard that people are already somehow managing to snake.
The tracks themselves are great when you actually RACE (in time trials) and I want to unlock all the racers so it's very addictive. So I don't know if I love or hate the game. I think I hate it so much that I want to beat it. I'd love to know what everyone thinks about it when it comes out in the USA...
The wheel is pretty terrible due to the fact that.. well, it's a floating wheel. you end up crossing your arms and getting into a terrible mess just trying to steer correctly. You press A to accelerate still, so you're pressing your thumb forward into something you're trying to twist left and right. I have been using the wiimote and nunchuck which is a good control scheme. The only wiimote feature used is to waggle the controller to do a trick in the air. I wish the Gamecube was still alive, I haven't played anything but Warioware on the Wii that couldn't have been done on the Gamecube (and I would be $300 richer)