I will happily continue using iTunes over anything that uses a slice of citrus as the volume slider.
A nice operating system with a bad media player.
Not my biggest OS X annoyance, but easily in the top five.
I tend to control volume using the system's volume slider, the media keys on my keyboard and the hardware knob on my speakers. If I want per-application volume control, I can do that for all applications with pulseaudio. Clementine's volume control UI is very low in my application-choosing decision tree.