In a word, catchy. Even the hiphop stuff, which I typically hate, seems to fit in. There's a lot more space devoted to audiovisuals this time around, and some of the background animations are downright brutal as you try to match up the blocks. The most distracting one so far starts off with video of someone typing. You hear an old typewriter ticking away. Then everything gets all flashy in an inky sort of way, and you notice your blocks have letters and other characters randomly appearing in them.
One thing I like is that the normal singleplayer mode now has 3 difficulty levels right off the bat, and each one of them has its own sequence of animated skins and music. Once you unlock skins, you can string them together in any order and quantity you want, then go through your "playlist" once, or loop endlessly until you die. It's a nice evolution of the skins mode in the original. Lots of stats and scores are saved.
I've played for maybe 2 hours total so far, so I still can't form a completely valid opinion. But it seems to be perfect for anyone who got into the original, and is itching for more.