It used to be a really good firewall and its user friendly interface was why (the lack of frenetic pop-ups). But with the later versions it has become more bloated and is also crippled as far as outbound protection goes (In the Program Control, configuration area, the slider will only goes as far as Medium protection). This in the hope I'm sure of getting you to buy the pro version.
If you check the Pro version, "High" in program control says the same in "Medium", so there is no real difference in ZA free for program control.
I have ZA free on one computer & ZoneAlarm Antispyware (includes the Pro FW) on the other. I have about six months left on the free "patch Tuesday" special.
I don't feel any less secure with ZA free.
My computers haven't been compromised. What else can I say?
I'm happy with ZA free.