I hold Rhythm Heaven games to a high standard. The DS game became such a fixture in my life that it permanently wired rhythms into my brain. Months after the last time I picked it up, I'll still randomly "scratch-o, hey" or hit imaginary taiko drums in my head. I'm predisposed to seek music games with original music anyway (Parappa, Gitaroo-Man) as it is, and Rhythm Heaven is among the most replayable and content-rich of the genre.
So when I say Rhythm Heaven Fever doesn't quite measure up to its predecessor, please understand that's not a condemnation. I just mean it's merely wonderful instead of the most wonderful.
Though there are more than a few games I love and plan to replay obsessively, it feels like fewer than before -- and there are more this time around that I was just plain glad to be done with, and never plan to return to again. If I could buy anti-DLC that removed "Tap Troupe" from the game, I would. The existence of these hated tasks is a knock against replayability, as they reduce the in-game content I want to sink my time into -- and also prevent me from unlocking some of the "extra" games, as I'd need to do exceptionally well to win "medals" to unlock them. For things like Tap Troupe, that ain't happening.
Rhythm Heaven Fever demands exacting rhythm from its players, and goes out of its way to switch the beat on you, force you to perform multiple different rhythms in rapid succession, and obscure the on-screen avatar so you're forced to play by sound. It's much more challenging than you'd expect such a cutesy game to be. I think Nintendo took the change to precise button controls as an invitation to ramp up the difficulty.
In fact, if you approach it as a series of challenges to be overcome with skill, you will be driven into a rage (trust me). The correct approach is to just have fun, enjoy the funny animations and noises when you screw up, and keep playing until you can keep up with the rhythm naturally. I wish I could say I came to this enlightened approach easily. I was taking the whole thing way too seriously, getting far too irritated at the seventh "remix" stage (a new song that blends the previous minigames), and then I played a couple of rounds of multiplayer with my wife, who burst into laughter whenever she missed the timing. It was revelatory.
Fever includes, for the first time, a limited multiplayer mode, allowing two players to go through a selection of games simultaneously. This mode is a little disappointing, offering only eight minigames (and a few unlockable bonus games) and featuring the exact same songs and rhythms as their single-player counterparts -- just with two people playing. But it's still a chance to share the game I love with the people I love, and a total success in that regard.