I guess I'm one of the few left still using MSSE. I find that it's not a resource hog and runs silent. No nag screens to upgrade, it doesn't "talk", it doesn't expire and the price can't be beat.
I'll give clients the option of buying a product or using the free AV solutions that most most ISP's offer. If they can't be bothered it's MSSE which is also on my bench rigs. I don't sell AV/AM products anymore.
Spybot and Spywareblaster were some of the first anti-malware apps I used. I just cleaned a machine that had Spybot installed. I didn't realize it until I went to check the hosts file and founds hundreds of entries. I did like their Teatimer feature.