Yesterday, I finally managed to get through Wario's Gold Mine. The highlight of that race was getting hit by a blue shell right when I was on a turbo boost thing, landing at an angle, and then being immediately boosted right off of the track.
So I have unlocked everything, have gold in every cup, and am rated 1-2 star in every cup. I think I have 2 star in about 25% of the cups, but I am not about to try to go through and 2 star everything, even though I could probably pull it off without too much effort.