It's very much in vogue in the anime community to bash K-On! because it's supposedly shallow, has weak characters and a plot that's only there to show cute girls in various situations, but I thoroughly enjoyed it for it's high life escape value ^_^.
My current desktop background is this of Mio from the light music club. I guess it's a typical otaku fantasy to be friends with a cute, shy girl and I'm falling right into the nerdy anime stereotype, but I find Mio very endearing. Besides, it's a nice design and scales beautifully on my new 1920×1200 display. Or screen, or whatever it is this thing is called.