I like that it is very user friendly, has all of my tools needed to run our test suite in one place; plus some additional ones! It's not easy at first but once you get used to how everything works together there aren't many problems with this tool as far as functionality goes.
We use phpcitest internally so we can easily see what tests are failing or passing without having multiple web pages showing us different things from other CI systems which makes managing builds easier since they're consolidated into just 1 page (a dashboard).