Necro BUMP!
Started playing this again, and I'm really enjoying it.
I've yet to unlock everything, but it's mostly super heavy weights I'm missing and I don't use them anyway.
I'd say the least picked courses are Shy Guy Beach and Toad's Factory, while everybody seems to like Rainbow Road and the Mushroom track.
I agree with the above poster in that the weapons get out of control, but that's part of the fun of this game. Some of the straight away courses like Mario & Luigi raceway and moo moo Meadows are pretty much all luck with items.
Even though this game is 2 years old, it's still easy to find games most of the time.