So, I've put nearly 20 hours into Skyward Sword now and today, for the first time since starting mind you, I did have to re-calibrate the MotionPlus. It wasn't even for the swordplay, which was oddly still working just fine. Instead, the issue came up when I attempted swimming under water (an ability acquired a little while after completing the third dungeon). Just like riding on your Loftwing, swimming underwater is controlled by tilting the remote in the direction you want to move.
The first time I submerged, I found myself looking at Link in disapproval as he inexplicably constantly spiraled downwards. One quick calibration and all was right.
Considering the amount of times I had to calibrate the MotionPlus in Red Steel 2 and other MotionPlus titles, this one time in nearly 20 hours of the game is still an absolutely colossal improvement. Nonetheless, I'm still a little sad that I can no longer say that I've never had any real problems with the motion controls in Skyward Sword. Oh well.