I have made mine my go-to foam pad and a core component of my sleep system. I hammock, and when ground sleeping prefer to sprawl out a bit, stomach and side sleeping.
Generally I put it down in my shelter as a foam floor for my girlfriend and I to both lay on or sit on versus each of us carrying a Z-lite or pro-lite pad. I love the lack of a gap! On top of that we each have the klymit inertia x-lite pads, I have the torso one and she has the full length version. Never any worries of slipping off my foam pad, and the klymit pad adds a little extra for my hip and shoulders.
In solo use I can roll about the entire footprint of most 2 person shelters, or fold it in half lengthwise for a standard width, double thickness pad for more R value, and in half the other way for a four layer short length pad for REAL cold.
In my warbonnet double 1.7 blackbird it fills the whole pad sleeve in a way the gossamer gear thinlight wide hammock pad never could, making room for two cozy hikers. One hammock, tarp, sleeping bag and foam underpad makes for a LIGHT packing list, and this is now my go to summer setup with my lady.
The 40×80 configuration is honestly superior to the 20×72" pads we are accustomed to.
Prior to getting the multimat I was using the 60" by 40" gossamer gear thin-light hammock pad, I had mine cut diagonally on one edge, so it tapered to about 30" at the foot. The gossamer gear wasn't big enough for two person use IMO the added length is more useful.