I started using Comodo on single computer about 3 months ago (mostly because of Tech's continued recommendation) and have slowly rolled it out to the others. The most recent installation is 30 days old today. Other than that one small glitch with the registration it's been problem free for me.
If I have any complaint about Comodo I could wish for better logging options but, as Cloussau pointed out, that can be as much a curse as a blessing.
I can only compare Comodo to Jettico, Zone Alarm Free and ASahmpoo Firewall as I have little or no experience with Sygate, Kerio, etc:
I tried Jettico several months ago and at that time the pop-ups were endless. It never settled into a mode where it recognized what should and should not have internet access. I got rid of it after a week.
I've been a Zone Alarm fan for a while but lately I don't like some if the changes they've made. For example, ZA logs every program opened even if it doesn't want internet access. This makes working with the program control a little cumbersome.
I was also very excited about AShampoo when it first came out becuase it's so light on resources. But it caused boot problems on several machines that I couldn't resolve short of uninstalling it so I gave up on it after the first 3 revisions.