My team and I use GoRetro for team retrospectives at the end of each sprint. It allows writing feedback anonymously, commenting on the cards, "likes" and even gifs for a touch of humor. It does its job perfectly. Review collected by and hosted on G2.com.

Not much to say in terms of negative feedback. A small thing to be improved is that infinite "likes" are allowed per person for one specific card. This is just a minor improvement to be made, though, nothing bad, really. Review collected by and hosted on G2.com.