Well, it was actually several sessions play today, rather than just one long go, but I reached the end, defeated Dedede, and then beat Nightmare. Hurrah!
I noticed that the last level (the one in black and white) was actually some sort of medley of the levels from the original Game Boy Kirby game. I’d never realised that before. I just thought it was black and white for some sort of arty reason. It explains why you don’t get any power-ups from sucking in baddies, anyway.
So I’m 81% done. Most of the secrets I know how to get (I failed to reach them, or went past the entrance to them before realising what I’d done), so I should be able to get 100% if I want.
Oh, and a Bad Thing: Rainbow Resort (world 7) has a level with a SuckySuck(TM) bit in it. They’re not a load of end-of-world bosses, but there is a run of about 8 mid-level bosses one after another. Rubbish.