I was *just* about to come on here and start a new thread on the very same seat. Mine came last week and I've been riding it since (with some exceptions to take the street bike out with some buddies.) For using their own pan it went on pretty easy - a little bit tight getting it down and bolting it in, but nothing worrisome and no mods needed. (My under-seat area is generally stock - air box, etc. is still there although I've added a small set of electrical relays to power a few things and have a waterproof thing for my registration/insurance info.)
I'd agree that the improvement is real - I still feel some pressure points but it also could be foam that hasn't broken in completely. Up front it's shaped like the stock seat - still easy to stand on the pegs and move around, but if you slide back just a tad it's way wider and a more comfortable position for long pavement stretches. Haven't done any stretches much more than an hour (stock tank, so that's typical.)
My Alaska Leather sheepskin recently died so till that gets replaced I'll ride it bare. Definitely "slipperier" - I have some mesh riding pants with a really grippy butt that made it hard to slide around on the OEM seat so could be a perfect combo. With the "fall" pants on I did find myself sliding forward a little without intending to. The material looks tougher than the suede variants I hear about for other custom seats, I'd have no problem dumping this in mud and hosing it off. I'll be taking it to Moab in a couple of weeks, where mud is probably not on the agenda but lots of other abuse should be.
So to sum up - I'm a fan. Looks like an improvement and I had the same quick turnaround. (Although I never got a shipment notification - I was just thinking of pinging Sargent to see when they'd expect to get the seat out and there it was on my front door.) Got to keep my OEM seat, just in case, but not sure when I'll use it (maybe donate it to any buddies who want a Renazco or something.)