Yes, and exactly 3 times.
I have known K-ON! through Josh Agarrado when he played Tenshi ni Fureta yo! on the 피아노 (you can listen to it here:
link OI&list=PLFFEA0C01640D75C8).
I decided to listen to that song (with Eng sub of course), I cried when listening to the song and 읽기 the sub, because I have graduated Junior High School and had to say good-bye to all my close 프렌즈 from just a few months ago. The song really brought back our memories...
Then, I went on and watch the whole series. I fell in 사랑 with it, and cried 2 더 많이 times in episode 20.
P/S: I'm a guy, and I'm not the kind who always cry when seeing touching things, but I cried when watching K-ON! and another 아니메 (called Yuki no Joou - 또는 The Snow Queen), so they must be very meaningful and touching.