I like that it is free and open source, with a good supporting plugin base to expand its features. The support community is very helpful and engaging in answering simple questions about how to set things up to more complex questions, like how to debug a custom plugin or the code for customization. Review collected by and hosted on G2.com.
The documentation can be hard to find information in and is sometimes confusing or not complete. I think their complete rewrite of the administration interface was rolled out too soon, but they have done a good job of getting it back up to par with the old interface, although there are still functions missing, which have been left up to the community to fix. Review collected by and hosted on G2.com.