Since Karana23 has already explained basically all about Sygate, Im just going to write about my personal experiences with Sygate. Hope I dont bore you, lol.
I used to use Zone Alarm all the time cause it was simple and secure, but one day it started acting funny so I decided to re-install it to fix the problem (this usually would work) but it refused to install. To this day Im still not for sure why it doesnt want to install, oh well. After that crap happened, I started my search for a good firewall, after trying about 10 different firewalls and put all of them through my tests Sygate came out on top for stealth, ease of use and simplicity. Zone Alarm is still better for the average Internet user but right below Zone Alarm was Sygate.
Ive been using Sygate Personal Firewall for about 3 months now and it hasnt given me any trouble at all. It has blocked many attacks on my computer and has held strong. Its pretty simple to set up, simple to run and doesnt bog down my computer like some firewalls did. Sygate also doesnt slow down my Internet connection (which Im on stinking Dial-up so it better not, lol).
Well, thats about all I can think of for Sygate that hasnt already been said. Safe surfing everyone ^_^