They can start off by making their own products compatible with each other. Symantec is a bit of a memory hog, but I could live with that. The problem is when their firewall and A/V suites incessantly fight with one another, and refuse to be removed, you end up having a major problem on your hands. The free offerings from Grisoft and ZoneAlarm are a better fit for about 90% of users.
I have Norton Internet Security, it comes with firewall and Antivirus, works pretty well... I test it at grc.com(shields up) at it says true stealth
When I talked to a network guy a while back, he spoke of "demilitarized zones" and whatnot, and then said that his Symantec and (some other vendor--McAfee?) products were exchanging fire across the DMZ, and that he was requesting peacekeeping troops from the UN. :)