Here is my experience with the Digium AA50 over the past year.
It’s an Asterisk based PBX based upon the Blackfin processor.
It has all the features of Asterisk Business Edition in a small simple to setup package.
Base support is good but can take a day or two for a response.
Now for the cons:
Once a week the flash memory becomes read only and no can leave messages. The system then reboots itself!
I contacted Digium and they said it’s a known issue that will be fixed in a later update.
Another downside is that even though there is a WAN port it does not have any protection against SIP registration attacks.
Most PBX’s this size (Positron, Grandstream, and Yeastar) provide some level of protection.
When the system get’s attacked it can freeze up and/or stop accepting calls.
Hopefully these bugs will be fixed in a later release.