Well, based on the recommendations of both Lindy and James (who both were not looking forward to this game with the fanboy fanaticism I feel tends to make reviewers treat Nintendo games with kid gloves), I caved in and picked up Galaxy 2 today. I've completed World 1 so far with every star I can find (including the return of the...ugh...crate-breaking mini-game), and so far it looks to me like Nintendo addressed most of my concerns with the original Galaxy to make this quite possibly my favorite of the 3D Marios: each galaxy only has a couple of stars rather than half a dozen; the "open world" galaxies that were so terrible in Galaxy 1 seem to be (for the moment) gone; the galaxies seem to be a lot more creative; bosses are a lot more fun and interesting; and access times in and out of galaxies are a lot quicker. Progression all around (my biggest sticking point with the first galaxy, which I felt got bogged down by repetition and a certain amount of conservatism) is vastly improved, and the game is dramatically better for it. Also, I've run into 3 Power-ups so far: the Cloud Suit; the Drill; and (of course) Yoshi, and I really like all of them. Yoshi actually works really well with the Wii Pointer controls, and Nintendo did a really good job making him feel really powerful.
My only real complaint so far besides the insipid main story (I'm sorry, but I'm not going to let that go. It's been over 20 years and we're still doing this same shtick) is something I had major issues in the first game: the use of waggle for the spin attack. Yes, it kind of works, but besides the pointlessness of it I sometimes find myself doing the spin when I don't really intend to just doing a slight involuntary arm movement. It's not a major issue, but on occasion it has caused me to die (the galaxy with the flipping platforms triggered by your spin attacks comes to mind).