As some one who has been a very early cheerleader for Agnitum Outpost, and a registered owner for the last several years (and paying a yearly update each time), I feel an obligation to say I have removed Outpost from all of my machines.
The last update was the straw that broken the camel's back for me -- it slowed down my network traffic and pc *significantly*.
It's clear they are doing some ambitious things with their firewall, and i don't rule out going back some day, but i've had enough of the instabilities and slowdowns.
Up until recently i've been using the free Comodo Firewall, which is *very* powerful, but just today i installed Eset's new Smart Security suite which includes a firewall, and i have to say i'm LOVING it. It gets the alerts "right" (it allows you to quickly approve/block/customize a rule) in a way that comodo doesn't.
Comodo is a bit complicated, Eset's is a bit over-simplified and lacking options, but then again i'd have to say that Eset may have one of the most promising first firewall releases i've seen. If they keep tweaking it the way they have their antivirus, this will be THE firewall. It's already good enough that i'm buying it and using it for now as my firewall of choice.