I used to play the clarinet a little. What I found frustrating was the fact that it is pitched in B flat, so when everyone else is playing a C, you have to transpose or you are actually playing a B flat. That's just too much hard work for me, especially as I often would learn tunes on the recorder or tin whistle and instinctively want to use the same fingering on the clarinet. No problem with that until someone on a different instrument joins in! It's also what put me off the sax, which I love.