I too have used Barracuda and EVSA. I work at an ASP that hosts mail and we were an early customer of Barracuda. We have decommissioned our SPAM Firewalls, after melting down 3 in a year, endless issues with quarantines, and MTAs. My Engineers used to spend 2-3 days per week working on 'cuda related issues. The nail in the coffin was a call I had with the VP of Engineering. When you know what they consider a "stable" release of an upgrade, you will run away. They hide experimental MTA's in bug fixes, they deploy features arbitratily, and only recently figured out how to really "cluster" the boxes...there is just a lack of engineering discipline. Those large customers that they talk about? They won't move past there currently firmware versions...just too iffy. And a quick chat with anyone that knows spam assasin, can tell you that the number claims come wiht a lot of fine print.

I know more people leaving 'cuda than deploying. As for EVSA, after using EVSA, and seeing what many ISP's pass off as enterprise (qmail, though solid, is basically latin...) I would say that with a linux contractor, you could easily build an enterprise scale and have the flexibility to add/remove what you need, and the cash to train your folks on how to use and maintain it.