I have three installed, and, a fourth one is part of another program (Netscape8.1). My experience is:
1. Spyware Blaster blocks cookies to Internet Explorer as well as Firefox. and, it does a great job. No reason for scanning anything. But, no cookie no go. The program, periodically, updated, like all the others.
2. Adaware scans Registry and Files, and it finds all sort of stuff related to Internet Explorer, which I barely use. I have never seen it report anything serious.
3. Spybot Search and Destroy used to be my favorite, and on scanning it seems to find only cookies and cache in Mozilla and Firefox. Unfortunately updating it has been a bear. Yesterday at 1 AM, it took 45 min to install about 80% of a 1MB update. I gave up, and uninstalled it.
4. I have nothing pro or con the Netscape8.1 anti-spyware. It found all sort of horrible stuff the first time around ( not detected by anything else). I ignored it, and it goes on reporting all is well.
5. I had a similar experience with Windows Defender beta1 (i.e. nothing found). I did not upgrade to beta2, since it requires SP2, which I have been too chicken to install
UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.13) Gecko/20060331 Firefox/1.0.8
