From what I played with it I'd say the Heavy Twinfusor is actually on par with the X1 LMG. While the X1 is still silly good, the TF I find very good for dealing with lights who come to pester me as I shell the enemy base. Using the SF MKD you need to think about where you place the shot more due to the reload, TF I can spam a couple of shots in an area and I'm more likely to hit them, plus if you hit them with the double tap it will more then likely kill them. On heavies and mediums the X1 may be better in some situations, plus its obviously better at anti-air use. I played about with it on a Sunstar Pub match with the MIRV launcher and I was a royal pain in the gen room at times.
Also BPS! BPS everywhere!