The sequel, which came out about a year after the first game, is pretty much identical to the original in terms of modes, features, visuals, etc. The game has the same "arena" based progression system whereby you clear scripted challenges (such as "finish 3 songs at basic difficulty with a grade of B or higher") in order to unlock arenas (stages featuring different visuals that your character dances on). There are a couple of new characters and an option to use your Mii, which ends up being about as creepy as it usually is in these games. The Wii controls seem to work as well as in the first game, and the soundtrack doesn't seem to be noticeably much better or worse, although it does include a handful of music videos as some previous installments did.
There are apparently some other minor additions that are tucked away that I didn't really spend much time with, such as a mode where you can just watch (and presumably imitate) the dancers' choreography without any gameplay. There's also a somewhat weird "hand combo" that you build up by shaking the Wii controllers on the beat that helps boost your score, but it seemed like more trouble than it was worth so I didn't bother with it much. Otherwise the game is pretty much an expansion of its predecessor, which isn't a bad thing since the first was pretty enjoyable. There's a Dance Dance Revolution: Hottest Party 3, which I expect to be as similar, so I'll probably skip around a bit again before coming back to it.