I got it yesterday and fought through Subspace Emissary - took me about ten hours to complete with 80-something completion. As others have said, the controls are terrible for a platformer. But the story is surprisingly good - so good, that I was angry when they had a single inconsistency on what the powers of the bad guys were in the Diddy Kong scene (I think that's obscure enough to not be a spoiler).
That said, I want to talk about the controls a little more. In particular, I'd really have liked to see all the reviewers tell us what controls they were using. The vast majority of people don't have Cube/Wavebird controllers - remember, there are lots of new people buying Wiis - and just saying "use a Cube controller" is patently unfair. The game suffers demonstrably with any of the other options vis a vis the Cube controllers. I ended up using the Wii remote turned like an NES controller option - using the left analog stick on the classic controller is hard, because it's clear the placement is secondary to the D pad used for NES and Super NES games.
I believe that most reviewers still had Cube controllers lying around, so they did what was easy - instead of being a proxy for the gamer. Let me make my point clearly - reviewers have an obligation to review games under the conditions that their readers/viewers most likely will encounter the game under. I'm not saying they have to use a 480i 19" CRT or whatever - we don't have the data for that - but in this situation, they missed the boat. The manual assumes remote + nunchuck as the default, and I think reviewers should have used that as their playthrough method.
At least Kotaku, in their new love/hate roses/violets review did this. But it's not a minor nitpick - it's a huge, major issue in the game. The game could have remedied it in some way but allowing the D pad to be used for movement on the Classic Controller, but doesn't. But it's clear that they said, as did others, we need to note the point, but not suffer through the game because of it. It'd be like hacking Lair to not use the SIXAXIS controls. The game's not Lair-unplayable, but the game is poorer than Melee because you have to use a controller that NINTENDO DOESN'T MANUFACTURE ANYMORE to get full enjoyment of the title.