I actually didn't listen to all of it at first, lol. The girls are cute and that's pretty much why I just watched it. The singing is okay - prefer the middle girl's voice than the other ones. As for their arrangement, ehh, whatever.
I was too busy panting at the Minorin and Nana-sama part of the show....
Oh, uh,
here's that K-On! event where the seiyuu performed Fuwa Fuwa Time if you don't want to load up Rajion. :V