Here's mine:
BMW K75, K100 and K1100 "square" stock seats are simply awful. I did two long days on one on a K1100RS fly-n-ride purchase. By half way through the second day I had to stop every hour due to the ass pain. There is a special place in hell for whoever came up with that seat design. My butt hurts just looking at one of these. Zero motobirds.

The stock seat that came on a BMW K1 that I bought last year was similarly uncomfortable but an Alaska Sheepskin butt pad makes it a bit more tolerable. One motobird for this one. :mbird
The scooped out rounder
BMW "comfort" seats are pretty decent but built for someone with a shorter inseam than my 34". Three motobirds for this one. :mbird :mbird :mbird

My worst seat experience ever was
Rich's Custom Seats in Seattle. (Now Kingston.) He took a K bike stock seat and actually made it worse - which is quite a feat if you ask me. I then went back for a second whole day of waiting around to try to get it better. I told him it needed it be lower, more scooped out and farther back. He did pretty much the opposite (I think because he was too cheap to make another cover for it which is what he would've had to do to move it back as I requested.) It is nice looking though but it is the very definition of a polished turd. After wasting $500+ (I think it's $700 now) and two whole days I just gave up. I've run into a lot of people who are VERY satisfied with his work and power to them but I've also run into a lot of people who had experiences similar to mine. Given my experience, the price and the result apparently being a crap shoot I would never recommend him to anyone. Rich gets negative motobirds for all the time and money I wasted.
I've had several
Sargeant seats of varying styles. All worked pretty well. There were all in the three to four motobird range. :mbird :mbird :mbird :mbird
Corbin:Dual Tour: A pretty decent seat that I've put many miles on but made for someone with a shorter inseam than me. Four motobirds. :mbird :mbird :mbird :mbird
Dual Canyon Sport: OK seat. Better looking on an S or RS K bike. I run one now on my K1100RS - use an Alaska butt pad for longer rides. Three motobirds. Maybe three and a half. :mbird :mbird :mbird
Gunfighter: Looks good because the back of it matches the K bike tail cowl but way too hard for serious miles. Two motobirds. :mbird :mbird
Rumble seat: (The back part flips up to be a passenger backrest.) About the same as the Gunfighter. Two motobirds. :mbird :mbird

All of the Corbin seats I've had have been very heavy due to the fiberglass seat pan.
Russell Day Long: I've had several used ones. Most have been pretty good but were built for people with a shorter inseam. The most recent used one I got is an inch or two back compared to the others and is bar none the most comfortable seat I've ever ridden on. There is only one minor nit I have with RDL seats. When you're stopped at a light and standing you can feel the "wings" hit the back of your thighs. It's just a very minor thing but enough to bug me just a little. If I ever did an Iron Butt Rally it would be on a RDL. I've put several 14 hour days on that seat and its comfy even for that. This seat is the king with five motobirds. :mbird :mbird :mbird :mbird :mbird
Rick Mayer:Johnny has several and gives them rave reviews so I had one made last year when he was having a sale. The seat I got back from him was too high, too far forward and pitches my torso forward on a bike that's supposed to be ridden upright. (K1100LT) It would probably work well on my K1100RS but I wanted it for my LT (and that's what I sent him pictures of me sitting on) so it's just sitting in my basement. To be fair to Rick I have not had a chance to contact him about getting it better dialed in (plan to finally get around to that next month) so my jury is still out on Rick Mayer. Motobird rating still pending....