this game is alright..though the only thing really "new" about it is the use of the wii wheel..while in itself can be a pain to use.and with the choice of a classic kart or a speedy bike to use. karts get better top speed but bikes deliver control and drift and the new pop a wheelie option,which can get you ahead.
the new tracks are somewhat unique while others copy a previous track.hence the desert level dry dry ruins and rainbow road (classic finisher though) this rainbow road isnt for beginners. its a tough one!
the retro cups arent bad either..they brought back some good tracks.
my favorites are coconut mall and koopa cape.
the only way to get anything is to play it excessivly and very well. like most things are unlockable by playing 100s of races and getting stars on all levels of all cups.obviously theres more characters and vehicles.

the online play is somewhat ok though alot of times if your a newbie you'll get thrown in with people who have 8000 points. I only wish if you werent happy with the chacater you play as that you could change it but you cant unless you quit and return to the main menu.