A firewall/router from designed for a Small Office or Home Office. It is very similar to any other router you could find at a computer store - the Linksys, D-Links, SMC, etc with more features like logging to syslog, VPN support, and advanced NAT. The unfortunate thing is that the majority of small/home offices don't need this stuff. With the Firebox SOHO (including VPN option) being up to 8x the price of a cheap one, it probably isn't worth it for most SOHO applications. The only really useful application for it that I can think of is if you want to VPN with a central office that has a Watchguard Firebox II.
My last big beef with WatchGuard is that when you get the box, you get absolutely no documentation, only a card that tells you where to go on the internet to get documentation. This page actually tells you to print out the entire PDF installation manual because obviously you won't have internet access as you are installing the new router.
As much as I love Watchguard and their other Firebox hardware, I gotta say that you should really save your money and get a cheap one from your local computer store.