Another thing to consider which I only came across very recently, is it the way you ride? I have a Fizik Arione and find it very comfortable, last month I did just under a 1000 miles on it, 7 of the rides where over a 100+ miles and I never had a twinge from my backside. The week before an event I took it easy and did a 70+ and a 40+ ride, trying to keep a very low heart rate and not be too tired for the event, but on both these rides, my backside was killing me after only about 30 miles, I just prayed to get home it was that bad. The difference between the rides was on the long ones, I was pushing hard and constantly changing position and standing to cycle, on the easy ride's, I just sat there and spun and hardly moved at all on the saddle, so perhaps moving about on the saddle a lot may be instrumental to having a good ride, perhaps it helps the circulation constantly sliding about and standing up.