This is slightly (almost completely) OT as the question is prompted by the behaviour of Rhythmbox, but I think I can squeeze it in here. Please shift it somewhere more suitable if required :-)
I've found that most of the time I settle on a "rough" volume and then want to refine it a bit depending on the track. Sometimes the standard increment / decrement is too coarse; sometimes it may be fine enough, but it's hard to fine-adjust because it takes a delicate touch.
So is the minimum increment / decrement ultimately determined by hardware, and if so how coarse / fine are these tyically.
In the case of PC based software I always find myself wishing there were two sliders; one to get you to around the right level and another to vary up / down around that baseline by, say, 10% of the value in either direction. Or do I just have bananas for fingers and cloth ears?