OK, and here it is: I got back today after my installation at Bill Mayer's in Ojai on Friday--a 400-mile ride one way. I've heard a new seat needs some kind of "get acquainted" period before you really know, but I DO know already--I like it. Of course, I've been on a stock seat, and that's not hard to beat. Maybe I'll keep liking it more and more as I get more used to it. Hope so, but it's already very comfortable for me.
As to the material, I went down with an open mind. They offered both smooth leather covers or vinyl in either smooth or basket-weave. Pros and cons: vinyl is hotter and "sweatier" than leather, with the basket-weave being cooler under you than smooth. Leather is the coolest choice.
Durability: he said it really was a push. Barring vandals with knives, the seat isn't going to wear out, whatever cover you pick. Whatever you choose, you'll be living with while you have the bike.
Maintenance: the vinyl is maintenance-free, period. Leather needs to be conditioned occasionally. He gave me a bottle of stuff to rub on every few weeks, more in the first couple months. No big deal. It's about as complicated as rubbing on hair gel or something, just give it time to dry, like at the end of the day. Apply it and let it dry out of direct sun. Easy enough to do. If the leather seat gets wet, don't let it dry in direct sunlight either. Drying too fast could make it get stiff.
I thought the leather looked and felt the best, and that's what I bought. I keep my bike covered so it won't be sitting in the rain, or even sun. Overall, I don't think it really matters very much in practical terms--just your preference.