I still think having two threads for K-ON is completely retarded, but whatever. If a mod feels like it he can merge this.
I liked the first episode of the new season - one of the best episodes so far. I dislike the OP mostly because in my opinion Toyosaki Aki's voice really doesn't work in that style. I'll probably warm up to it with the time passing, same as with the first season. ED is pretty nice, nothing special but good enough.
Anyways, K-ON was never a show where the music itself had too much meaning, and if you're expecting it to suddenly focus on performances, then you were watching different anime than me all this time. This is a show about girls being in a a school club, not about girls playing music. Feeling frustrated because it's a not the show that you want means that maybe you should just watch something else.
That said, it's entirely possible that music will slowly start being more important - or at least stop being cut out. They have to fill 24 episodes with something, after all.