It adds to the experience, if you ask me. The point of sharpshooter isn't necessarily about being on even levels with every gun, but more of a gametype for people who are good to adapting to new guns. The only real problem I could see with underbarrel attachment is noob tubes, and everybody has them, so it's not like it's unfair. Besides that, noobtubes are rarely ohk's on black ops (Or maybe that's just me - but it seems like whenever I get shot with a noob tube, flak jacket or not, I can still manage to kill the person tubing me).

But, back to the point, if there is a noob tube attached to the gun your on, try getting somewhere where it's hard for you to get noobtubed, i.e. the sniper's nest on Firing range, the radio tower on array, and so on.