No more airbursting the c4! It must come in contact with the ground/walls/ect first in order to activate it.. But in exchange the blast radius is supposedly bigger and it also turns into a motion sensor kind of thing when people are standing near it... Which can be useful in a few ways. Being one of those annoying C4 guys before joining CAG I think I'm more happy than mad about the nerf xP
The motion sensing thing can be useful if camping to watch a doorway or something.