I like that everyone even remotely can fill it out. They have a lot of different retro options depending on your team. We use the "what went well / what could have gone better / focuses" method and there's a bit of editing you have to do on the columns, but it's pretty easy. Plus you create a new retrospective each time, so each retrospective is saved if you ever want to go back to it.

My team was doing a retro with pens and post-it notes for a long time, which made it difficult for anybody calling in to participate (it was also kind of wasteful, honestly.) Since we've been using this tool, it's become very easy for everybody to participate easily, and we're killing fewer post-it trees. Plus, it's really intuitive and easy to use.