Retrium comes with great UI. The various features are really helpful in keeping track of the action items. Have been using it to analyse the sprint activity. Review collected by and hosted on G2.com.

I can not find much drawback for Retrium. But there was a scenario when I was in a team room and wanted to create another. But to do so, had to close the open team room. So, I think this is one thing could be added as a feature or if it's available then can be placed better on the screen Review collected by and hosted on G2.com.