That it has so many features including ones we never use. I also appreciate Arbor support and their usually quick response when we find a bug or problem. Ed and Eric Lomax have been particularly responsive. Review collected by and hosted on G2.com.
The bugs. For example the Arsonist process has ground our DDoS protection to a halt and the bugs we find tend to crop up again. I found a bug in the REST API that was only recently fixed. We usually don't find these problems until they become a major issue. Review collected by and hosted on G2.com.
