Those knobs are the weak link of the RA150 for sure, and the main reason to never buy a pre-owned unit no matter how tempting (the other being that the amp is quite affordable brand new).
Having said that I don't use them, as I have a balanced tube preamp in line with it so I just leave the volume of the RA150 set at 1pm or whatever, and control the output with the preamp. They are an economical way for Alesis to keep crosstalk to a minimum on an integrated balanced/dual mono speaker amp, but I have fantasized about bypassing them (essentially converting the RA150 to a pure power amp) more than once since I installed the preamp.
So in answer to your question... yes, they can be a bit annoying if you are using them as your main attenuation controls but it's not that hard to get used to them.
Edited by grokit - 5/18/13 at 3:15pm