If a group of high school girls in a music club having fun is your kind of thing, then K-ON! is for you.
This is not quite my sort of thing. On the other hand, K-ON! is very much in the vein of anime such as Azumanga Daioh or Lucky Star, with amusing snippets from the lives of a group of high school girls and even the requisite friendly female teacher. And this totally works for me. (I do wonder at the dearth of similar anime with male students …) It’s a little different in that the girls actually have something in common, though. I.e. they’re in the same school club.
If you need something amusing to watch, then I do not think the thirteen episodes of K-ON! would be a waste. Perhaps people that had been in easygoing school clubs might get much more out of the show.
There is one thing that I have to go along with the masses: Akiyama Mio is just so cute.