SpywareBlaster is deffinately good, it prevents the stuff from getting in instead of trying to remove spyware that has already gotten in. I would say get SpywareBlaster and then use a couple scaning programs like Spybot and AdAware to scan once in a while to check for anything that has gotten past SpywareBlaster.
But ever since i installed SpywareBlaster I havnt gotten any spyware at all and its been over a year. I used to have to reformat about every 6 months to keep the computer running smooth without spyware but not anymore, its great.