I have used the Norton Internet Security 2005 and have the following to share :
Its better than ZoneAlarm as it comes integrated with their Norton Anti Virus software.
All the bugs including any licensing issues get fixed by the technical support staff and the site has all the fixes listed to it.
The only problem is getting it to work for the first time. Once everything is turned out it should stay that way for a long time. Also there are many features which could be better explained helping you toy around with them. There should be more help on usage and best practices to be followed on their website.
The other probelms you might encounyer are the innumerable security alerts which you will be bombarded with making usage a hassle. So there is a lot of fine tuning that needs to be done on this software yourself to make it comfortable for usage. Most of the time the alerts are all harmless so you need to make sure they dont keep appearing often for certain usage and doing this can get a little tricky and messy. The help and manuals can take a lot of time to understand for this particular product as each product tries to come up with its own set of vocabulary to deal with the same problems users face. SO unncessary time is spent in trying to udnerstand their jargon and if you got the best in terms of security after reading on firewalls.
Also Symantec could have tried more to educate the customer in terms of best practices while using the product and more help on fine tuning the product apart from the customary help that comes packaged with this product.