It depends on the aircraft:
As far as commuters go, I've only flown on one once. About three years ago I had the pleasure of flying on a brand new Dornier Do-328. The Do-328 is one of the most advanced commuters out there, it's only real rival is the much larger Saab 2000. It is very fast (w/ a tailwind we were cruising at 405mph), quiet, and overall quite comfortable. Even though I had one of the engines less than 6 feet from me, I had no trouble sleeping and we had no problems with turbulence. I honestly would not mind flying on one of these planes again.
Then again, I have flown on several private aircraft (cessnas, pipers, etc) and they have much to be desired. So, once again, it all depends on the aircraft. Try not to worry to much though.
