BFBC2 only took a few hours to unlock damn near all the weapons - and even then the majority of stuff isn't worth using. I am sure the same will be said with BF3.
Well, it wasn't anywhere near that fast but I agree it wasn't exactly a ridiculous amount of time either. It was probably about 20 hours of time but most of the weapons were simply sidegrades that sacrifice one stat for an increase in another. There were some balance issues but it wasn't due to DLC guns or anything.
I do think this sort of crap is lame but unfortunately its what EA seems to love these days. Personally unlocks have lost all meaning, I remember auth'ing my EA account with Dead Space 2 and getting so many unlocks at the same time that it was just pointless. BLUE DRAGON ARMOR, SER ISAACS IRON JOCK, blah blah blah.