Sleekplan deserves 6 stars
6 stars is what I give Sleekplan. I use it as a feature request board to give users of my company's product a place to request, discuss and vote on new features and improvements.
There are so many things that impress me about Sleekplan; anonymous voting WITH moderation (so users don't need to register and can submit feedback painlessly BUT admins get to approve everything first, so no spam slips through the cracks), standalone website AND in-app widget if you want to bring your feedback requesting/voting inside your existing app or website, custom HTML to add personal (in my case, company-branded) elements to the board including custom CSS styling, and much more. So much more.
You get all that for about 20% of what other companies charge -- I pay $15 per month for more features than I'll ever need to use, and it all works so seamlessly.
The other thing that impressed me is the CEO (Marco); he actively takes requests to improve his product and then delivers exactly what you need -- this has happened twice now when I was looking for a way to do something. He just added the functionality I wanted in a matter of days. Super responsive to questions too.
So, all in all, you'd be foolish to look elsewhere. I'll be recommending Sleekplan to everyone who asks about a feedback or request board, and there's a month-long free trial that allows you to use the pro plan for free (no credit card needed) to see if it's got the functionality you need (spoiler alert: it will!).