I had the stock, Seat Concepts kit, and Renazco seats on my WRR.
When I road around town the stock seat was bothersome after about 20 minutes so I went with the Seat Concepts kit and everything seemed to be fine. Did a lot of DS riding in the area and life was good.
Then I went out to Colorado and rode the COBDR. There were some stretches of road that required some seat time as opposed to standing up or getting off the seat. After about an hour of riding my tail bone would begin hurting. Once I got back I was 'sensitized' to that tail bone pain and noted that it would start to act up within 15 or 20 minutes when I was riding around town.
My buddy has a Renazco seat on his WRR and we had swapped seats for a couple of weeks and I really liked - it no more tailbone pain. So I bought a stock seat and sent it out to Renazco and once it came back I sold my Seat Concepts seat.
Life has been good since.
I think the whole seat thing is a rather personal experience/issue. I generally like firmer seats and my Renazco is firmer than old Seat Concepts seat but I know people that cannot spend any time on a firm seat without some pain.
Unfortunately I think at the end of the day each person has to experiment around and sees what works for them. In my case I was very shocked that the Seat Concepts kit didn't work out on my WRR since I have used their kit on my KTM 450 EXC and my Beta 520 RR and have been very pleased. But then again I am usually not sitting down on those bikes for long stretches of time like I was on the WRR in Colorado.
One thing I have noticed is that as I have gotten older my backside has become more sensitive.