I've been on Fine Art America for a couple of weeks now and I'm so happy that I joined. I haven't sold anything yet but the atmosphere at the site is so stimulating between the discussion forums and groups that I feel inspired to work even harder on my art. It is also wonderful to be able to see what other artists are doing. I'm pretty isolated from any "art scene" where I live so this is a good experience for me.
I'm looking forward to a long and happy membership. And hopefully I'll be able to sell something too.