I will be the first to answer :)... Watchguard, Sonicwall, & Barracuda... Why? Cost of product, renewal, and support was expensive. Tech support for all was lacking greatly. In one instance we had a customer with one of these brands told to flash the firmware and when the system died as a result of the firmware flash the vendor told the customer that the hardware warranty was up so they would just have to purchase a new system. I won't tell you what vendor but I will tell you at the time the new system was around $6000. We have looked at the technology used by the vendors above and they are all built on similiar platforms that ClearOS is. In fact, many of the open source technologies that ClearOS uses are, also, used by these vendors. Yes it is true, ClearOS uses SpamAssasin and so do the vendors mentioned above (A small example).

Personally have successfully watched ClarkConnect / ClearOS replace the following vendors products - Cisco, SonicWALL, Microsoft, Symantec, TrendMicro, Barracuda and many others... the important thing to remember is this was done on one X86 box and uses one simple, integrated, intelligent and web-based interface to manage all of the network, gateway and server components for up to 50 users per single location. Environments ranging from Healthcare, Daycare, Education, Insurance, Church's, City's, County's, Construction, Mortgage and this list continues to go on... But you know me, I am sold and committed to seeing the world adopt an open, free and feature rich offering such as the one ClearFoundation represents.