I've played for around 4 hours now, and completed 25% of story mode. The gameplay is lots of fun, the level design feels perfect, and the boss fights have been cool. Only thing I'm less pleased with is the "combat". I miss bashing things with Kirby's various copy abilities, but I guess Return to Dreamland will satisfy that desire nicely.
I've tried all the mini-games and so far, my favorites are Brawlball (pinball) and Strato Patrol EOS (vertical scrolling shoot-em-up). I haven't played a pinball game since Pokemon Pinball (GBA), so Brawlball really hit the spot. Strato Patrol is pretty easy but really fun. Once you accumulate several Kirbys and a few powerups, you'll totally fill the screen with bullets and slaughter everything. Being overpowered is great! I kind of suck at shmups but I managed to beat Strato Patrol on my first try.