What I really liked about ZoneAlarm wasn't just that it was a very nice technology - and it was; but also that it got the user expectations and training right from a very early stage.
It was quite insistent on the fact that it would be "noisy" at first as it queried all the programs you ran, but would then quieten down once it had been "trained". It got that across in clear, simple language.
I think it was so successful because it got the soft side of its security job right as well as the hard part. It's certainly why I recommended it to anyone at the time...
Was working as an IT consultant. We got a call from an international manufacturer in the area for support. Local lead IT manager took down the firewall which infected their computer network around the world. All they wanted were bodies to help clean systems and apply OS updates.
My personal computer had ZoneAlarm on it. It became ground zero for reporting about infected systems. They ignored systems they thought were save; CISCO phone system running on Windows server and other backend devices. The company then bought a few licenses to run their own laptops.
It is such a same that Microsoft destroyed _ERD Commander_ and other quality tools which assisted in the clean up.