I've had a fair amount of experience with McAfee and I am overall satisfied with the program. I know that there are a lot of people that live by Norton, however.

Micael brings up some very good points about McAfee - most of all, it is a processor hog, especially on a system with just a little bit of age to it. A previous update of the McAfee scan engine caused major problems with slow downs and processor utilization time - McAfee has since posted another scan engine, which fixed the problem for the most part, but it's still a hog of processor. If the machines are older machines, you may want to look elsewhere.

Other than that, McAfee does offer frequent updates to both the .dat files and the scan engines. Overall, not a bad AV program.

I've not had experience with the others, so maybe someone else could provide some insight here?