I generally use unlocks wherever possible, with the exception of my PKM on smaller maps. See, the PKM only really works from prone, but the defaults work from standing or crouched.
However, I HATE the default SMGs as AT, and can rack up kills with the DAO12.
I tend to only use the PKM on maps that don't require a lot of movement on foot. With the PKM, I can hold a point pretty much indefinetly until some twat with an M95 snipes me.
Also, anyone who whines about the unlocks being 'noobish' is an idiot who can't adapt. Much like all the infantry-only servers, hackers, stat-padders, vehicle whores, griefers, and people who complain at me for trying to actually WIN.