As it gets colder, I appreciate the ION Fuse more and more. Last week I asked someone for a zip and didn't pay attention to check to see if I was zipped all the way. While on the water I noticed I was getting wet every time I dunked. I thought that perhaps I was experiencing a defective zipper. I stayed out awhile and though my upper body was quite damp, I was still cozy warm in 42 degree air temps and 50 degree water / waves /overcast damp day. I decided to come in and check on things and it turned out there was at least an inch opening from the end of my zipper. My "helper" didn't zip me in all the way. Well I remedied that and back out I went. Wet as were on the inside I still remained warm - I was layered with thermal underwear top and bottom with a fleece top...actually I was almost too warm so the dampness actually helped moderate my body temps a bit.
Last Saturday I was out on the water for @ three hours / air temps @ low to mid 40's Sunny. I was layered with thermal underwear only - cozy warm the whole time. My friend who was wearing a NPX Lucifer commented on being warm until he plunking around in the water. That was when he would feel the chill. Admittedly he wasn't layered all that much, but this is the fundamental difference between, and the advantage of the Fuse. The Fuse unlike the "baggy" fabric suits has an actual thick neoprene layer for its skin (4 mm). I at no time felt chilled while "soaking" in the water. I imagine you can counteract this by layering up a baggy style suit, but no matter what you do, you'll never have that neoprene insulating layer.
I'm sold on the Fuse. It's the best of both worlds > a drysuit merging with a wetsuit. And, let's not forget the virtue of having a Pee Zip!