First, I'd like to say that I enjoyed K-On!. It had great art, great animation, great music, and great voice acting. It had some really nice episodes, and it got me attached to some of the characters (especially Azusa). However, good points aside, there were also a few things that I disliked.
When I started watching this anime, I wanted to see the girls actually get involved in their hobby. Instead, I got a ton of slice-of-life scenes where the girls did nothing but eat cakes, do various schoolwork and visit various places (now, I do not mind slice-of-life, but I do mind it when important character development gets sacrificed for such scenes). And in the end, the girls were magically able to play their instruments perfectly and hold out concerts and stuff.
Unfortunately, playing in a band doesn't work that way. It takes
years for a person to become "pretty good" at playing an instrument (and it takes a while for beginners to get used to playing in a band). The producers got away by playing the "Yui is a genius" card in the first season, which lacked realism and was pretty unfair.
However, the situation becomes even more unrealistic if we talk about the songs they played. How did they manage to compose so many of them? Because once again, it takes
years for someone to become good enough in music theory, harmony, counterpoint and all that stuff to compose something decent. Did the musical scores appear by magic? Did the girls just play the songs by ear?
It seems that not even the producers know the answers to these questions. Maybe that's why they just tossed away the music aspect and focused mostly on the slice-of life scenes (especially in the second season). Oh, well...
No, I'm not going to rate this.