This was kind of a painful one to take for the team. I did choose to because I was figuring that the difficulty would be Mario Mix at the least and I actually do enjoy Mario Mix. I'd say the game's biggest saving grace is that hand markers were charted insanely well in this game and were very fun on practically every song. I'd say a good mix for two kinds of players actually, 1. Kids who've never played DDR and like Disney and 2. Believe it or not, people who want to learn hand markers in a less intimidating game.
Otherwise, if you're a foot only player whose played the other games even semi religiously, don't even bother with this. You won't get anything out of it.
About unlockables. Pretty much everything is unlocked, I did Groove Circuit for the second time and unlike HP1 and 2 it doesn't unlock anything else. So basically, the first run through unlocks everything and the second is just for completion sake. No Advanced Mode, no Training Mode.