It's vinyl, but doesn't look bad I've got about 2K miles on mine I picked up a deep bucket off the forum for my RK. Gotta say I love the seat over stock. (although I think I had a lower profile seat than stock on it when I purchased the bike)
I love mine. And more important, the wife does too. Yea, it doesn't look as cool as the stock seat, but I'm getting old enough that comfort supersedes ascetics.
I had a Sundowner on my '04 RK Custom. I had it modified to move me down and back because I did not like the seating position it originally gave me. The one thing that bothered me is it seemed to hang over the side covers and scuffed them up pretty bad. I pretty much cruised around with my C&C Solo unless I rode 2-up.
I have a Sundowner on my new bike but don't like the way it looks so I'll probably either go C&C or have my stock seat modded.
My wife LOVES the Sundowner. I can't say I did/do.
I had a Mustang wide tour on for 67000 miles on mine and just put on a Sundowner and it's pretty good i have to say...Very satisfied...it was a used seat also...