I used webroot's Spysweeper for about a year and I really liked it's performace. I switched to Microsofts Antispyware since then because I wanted to see how that performed, so far I havent found a reason to go back to spysweeper and pay the fee that they impossed.


PCMag.com review of Spysweeper: http://www.pcmag.com/article2/0,1759,1879982,00.asp