Cool technology, bad marketing.
I've had no issues with this software until one day a couple of months ago, it started quitting every 90 minutes.
For a couple of days, my email communication (and therefore my business) was in disarray, our service tech worked 10 hours to provide a fix which was to automatically start the server when it went down. When I got around to investigate the issue, I noticed that Stalker chose to build a time bomb into the software to make it expire on a certain date. If I had gotten any advance warning that it was going to happen, I might have found it acceptable. Unfortunately, the System gave no warning, the UI shows the license keys but does not decode them, so you do not know what you have licensed and when it is going to expire.
Since then, I contacted Sales twice to get a proposition on how to extend my license and no reply.
So, I now am an ex-customer. Other solutions, including Apple's Mac OS X Server Tiger, offer almost the same functionality at no extra cost.
If you do not need ISP class service and are prepared to pay big money for it, stay away from Communigate.