The only way I've been able to describe K-ON! is a little Azumanga with musicians (like Beck). I enjoyed the first season a good amount but I wasn't itching in my pants for season two at first. I didn't like how the characters didn't seem to original or fleshed out, some had personality quirks I couldn't get over and never got really explained. I didn't know what to expect from season 2 but more of the same.
K-ON!! or the second season actually does a great job in working out those personality and interaction issues I had with season 1. Each character has a more likable personality, yet unique in their own rite. The characters all seem to "progress," or grow up if you will in the second season in terms of how they're portrayed, but they don't lose the fundamental of what makes them who they are. It's very refreshing and in my opinion makes the second season much more enjoyable.
Not everyone will like K-ON! though; a colleague had explained it well to me: it's enjoyable if you spend time with friends. Those that don't have friends or don't really hang out with friends generally seem to lack the same enjoyment nor are able to connect with the characters in the series. To each their own I guess.
The new music introduced in the second season involves more than "Fuwa Fuwa Time" thankfully.
