I haven't used it (for any of my sites), but a site that did a Show HN yesterday (http://instantname.me/ http://instantname.me/) used https://www.uservoice.com

I haven't used it (for any of my sites), but a site that did a Show HN yesterday (http://instantname.me/ http://instantname.me/) used https://www.uservoice.com https://www.uservoice.com which I liked.