I never use spyware software on a constant basis anymore, after I educated myself how to surf safely on the net.
With Firefox, a real tough way to get past is to look into getting these addons:
-Adblocker
-Flashblock
-NoScript
-Greasemonkey + Stylish + ad blocking per Gozer (This is very tough!)
You could even install them all, and nothing could virtually penetrate your defenses unless you allow them to, actually you'll have to start allowing some things past and you have to be computer savvy to understand what you're filtering through.
IE has next to no defense built in or addons aside from popup block and phishing check.
As for a recovery service when somehow the machine gets spyware infested.. usually I resort to three main pieces of software rather than the common AdAware/Spybot pile of stuff (I'm a geek, I prefer to fix the source directly than having a program do it)
-Hijackthis
-BruteForceUninstaller (another software from Merijin of Hijackthis)
-ComboFix <- Really good, used this at work for the 1923801923 infested machines I worked on. 99% success ratio of getting off what you wanted.