I've been using NIS 2005 for 9 months and it works great for me. I've used Norton NIS for 4 years.............No problems and it's caught numerous virus's and attacks. I use several other Norton applications(Ghost, Partition magic, etc) and I"ve had NO problems with any of them.
I have friends that have been nailed using either Zone alarm or AVG while I'm smiling all the way.
IMHO NIS is getting a bad rap............