I used to have one, but I stopped using it and just went back to the stock seat.
I liked the extra padding and height, but I got tired of my ass getting wet every time it rained or got damp. There's no way to waterproof it and it soaks up water like a sponge. Plus, I like the way my pants kind of stick to the stock vinyl seat instead of sliding around on the Coleman/Stearns seat cover.
It did make a difference in comfort, but I rarely ride for more than an hour at a time without taking a break. They're very easy to take on and off, so it still wouldn't take more than a couple of minutes to put it back on if I wanted it for a longer ride.