Sorry for the bumpage but I was just playing around with this on a map that uses low-friction and I found that it has an interesting side effect. Icy areas that were meant to be very slippery actually became less slippery than regular floors.
I've attached a map for easy comparison. Load the attached into GZDoom without nashmove and see how slippery the central area with the SHAWN2 floor is then try again with nashmove loaded.
I also tested it with "sludgy" friction floors and it seemed to make things a bit more sludgy. It certainly didn't make them any less so anyway.