A lot of people seem not have not had problems; it seems to be developers and AOL users who are having most issues. ASP.NET is being reported as not working, for example. Some users have reported that the new ZoneAlarm has silently turned off some of their antivirus protection and at least one person has reported ports being opened they were unaware of.

Here's a few quotes:

"Users of Norton Antivirus Software, MacAfee Software, IIS (Windows XP), Visual Studio.NET etc. (the list goes on) and many more are having HUGE problems with ZoneAlarm 5.0."

"I think I saw this in another post, but I installed the latest Zone Alarm (zlsSetup_50_590_015.exe) and ASP.NET totally stops working. I can't get into my web projects, and IIS won't even serve them. Zone Alarm won't ask me any questions to correct it either, even after a lot of fiddling in the Program Control section. It just silently blocks something that ASP.NET needs to work.

Please don't release stuff like this. Keep it in beta instead of wasting our time. At least put a big warning with known issues on the install screen."

"After upgrading with, by now famous, 5.0.590.015, my ICS doesn't work anymore. Before this, I had a happy configuration with W2000pro like ICS gateway, ZAPRO (paid!), and W98 clients.
All the settings are identical with the previous ones, only shutting down ZA resolve the problem. I've tried medium @ internet zone, 127.0.0.1 @ trusted, DNS outgoing fine..."

" a good number more will be using it and not realizing that there AV software is no longer giving them e-mail protection - considering that the most popular AV out there is Norton's!- SCARY. "