I picked up my 919 last Sept. and have ridden about 3k miles on it so far. I almost made a post at one point about how much I LIKED the stock seat, so I guess it really comes down to different people’s preferences, though size and riding position, etc. might have something to do with it too. I’m 36, 5’7”, ~150 lbs.
I have chronic lower back pain / tightness. I also like to take long-ish rides of ~150 - 250 miles regularly, which makes managing that discomfort a challenge sometimes. In the past I would generally stop every 50 miles or so for a couple minutes (or more) to stretch out my creaky back.
My other bike is a ’01 Suzuki SV650 (‘S’ style with clip-ons for its first 11 years and a naked bike with a handlebar as of last summer). The bike I sold in order to make room for the 919 was a Suzuki S50 Boulevard (i.e. Intruder). I found the stock SV seat to be fairly uncomfortable. I bought a gel seat for it way back in ’01 or ’02. That still didn’t do much for my back pain. The stock seat on the Boulevard is a brick. I splurged on a Corbin Gunfighter seat soon after I bought that bike, which unfortunately wasn’t much/any better for me, at least as far as my back tightening up on me during longer rides.
Anyway, my point is that between these 3 bikes that I’ve ridden over the last 12 years or so, the stock 919 seat is by far the most comfortable for me. I find myself extending my time between stops to 75, 100, or even 125 miles or so. A few weeks ago, I was a couple miles from home after a ~235 mile ride, and I was going out of my way to add a few extra detours just to extend the ride a little. On the SV or Boulevard I would have started shortening the route and counting the miles to home 100+ miles ago, if not sooner. I’m really not sure if it’s mostly a matter of the 919 seat being the right level of cushioning for me (i.e. not too firm, not too soft), or if it might just be that this seat doesn’t force me into a more restricted riding position like the smaller SV seat and the contoured Boulevard Corbin seat. Maybe it’s a little of both. I know on the 919, if I start to feel some tightness in my back and hamstrings, I’m able to shift my position forward or back a little which I think helps me loosen up.