I like that they are very easy to use, have many options available (including an option if you don't want any of their features), but still allow the user complete control over what is being tested or reviewed. The UI could be improved upon in some areas - especially with regards to mobile testing/reviews. There can also sometimes seem to be lag time between reviews when using it from different locations which seems odd as this was not something we were expecting before starting our project. However once set up correctly, it has been working well since then. We're able to quickly test new builds / updates without having multiple people reviewing each change made by other team members. This allows us to make sure all changes go through one person who will ensure everything meets expectations so there aren't issues later down the line.