We've been using Features.vote for around a month now and I couldn't be happier. First of all, setting it up was really easy, even integrating it to our product took no more than 20 minutes. Secondly, our users love this. They feel like contributing to our product which is great because we also get valuable feedback. Finally, we already implemented 3 major features which were suggested by our users, thanks to Features.vote.
All in all, definitely recommend this product.