I've never used it. I'm a computer technician for a college and we provide Symantec Corporate 10.whatever.whatever which is actually an antivirus AND antispyware/adware/malware program all in one. I recommend using a program like this. Having multiple ones, or an antivirus and other antispyware programs can really slow down the computer and even damage the OS (generally only if you have two powerful AV programs running).
When I'm working with student computers that have spyware, typically an updated version of ad-aware run a few times in safe mode does the trick.
I've never installed any program but an antivirus program on my personal computers and I've never had a problem with spyware/adware. The safest measures are running Windows Updates, avoiding peer-to-peer programs and certain freeware, and using common sense when browsing the 'net (and opening e-mails or IMs from people you don't know). The only virus problem I've dealt with at home in years is because my husband tried to get a hacked serial number for a computer game and it was this site loaded with spyware that basically installed a virus on his computer. Afterwards he said he knew it was a dumb idea.