DH won't make you a FPS monster and probably won't impact your K/D ratio all that much either, but it sure as hell gives you the time to react better in every situation thanks to a much more accurate positional sound, because you can approximately tell where a threat is coming from and how far is from you.
Your skills, your knowledge of the maps and other player's weaknesses (and TEAM(WORK) >_>). That's what really makes the difference...Being able to pinpoint the enemy's location thanks to a more accurate sound, is just the icing on the cake.
It worked for me, on MGO, although that's not your typical FPS game...it's more tactical and slow paced. For example, with my old "all in one" headset I couldn't precisely pinpoint which floor other players were hiding. It was a muddy mess...but switching to the HD555 (plus the DSS obviously), I could finally do that and as a result my performace improved as well. With the DT990 it was even better, because I find it even more accurate than the Sennheiser.
R.I.P. MGO, btw.
Edited by Naingolann - 5/13/13 at 12:32pm