@Makeshift: What I mean by different modes is varying amounts of keys: for example, a four key mode that only uses 4 keys, perhaps a 6 key mode that does not use the spacebar. This would add some variety to the game, as well as provide a better introduction to new players. Someone starting out will not be able to handle 7 keys; it will be a very steep difficulty curve.
Now I'm also getting the bug with the instructions. And again, practice modes don't help: there's a reason why most games of this nature have modes for different button modes. (that being that different people have different preferences)
An option to remap the keys would also be nice.
If you want any chance of this becoming popular, add in modes that include less buttons. While this will appeal to the hardcore DJ Max and Stepmania crowd right now, it's way to hard for the average Kongregate member.