I've found K-On to be a fantastic light-hearted story with a refreshing lack of drama. I think the reason it's stood out so much for me this season is that the carefree aesthetic of the show is really quite refreshing. With other hard-hitting drama shows like Eden of the East are building tension and suspense through the whole episode, K-On gives an opposite approach, and really doesn't push any sort of seriousness on the viewer.
Ignoring the parameter of anime, even in American television shows these days, it seems like everything is over-dramatized and so many inconsequential scenarios are built up to
be a big deal. In K-On, nothing is a big deal - it's seriously just a half-hour spot of relaxing, fun enjoyment. This is the charm of K-On for me.
If you're looking for excitement on a Gurren-Laggan-esque plane, K-On is not going to give it to you. If you're looking for a panty-shot every other frame and an outlet to swoon over scantily clad girls, then K-On isn't going to give it to you (despite the entire cast being female, all of whom are absolutely adorable).
K-On is by no means a jaw-dropper, but there is a certain calm aesthetic about that I've never really seen in a show before. It feels good to watch a group of best friends getting along and playing music (or more often, eating pastries and drinking tea), so if you're looking for an easy-to-watch show with no hidden, analyzable motifs that simply exists to put a smile on your face, I couldn't recommend anything more highly than K-On.