Spybot Search and Destroy 1.3 is probably the best product for removing spyware and adware that other products can't. And it's FREE! I also use Ad-Aware 6 (free version) to get anything that Spybot might have missed.
Spyware and adware are wreaking havoc all over. The fact that so many products have come on the market to remove it is very telling. However, what is more telling is the fact that some spyware "removal" tools are actually spyware and adware themselves.
Now for your question. I don't have any personal experience with SpyKiller, but the name never came up in any reputable comparisons I could find. I work in IT and we have been doing side-by-sides with four different anti-spyware products. SpyKiller was not on the list. In fact, nobody I know has ever used it. Maybe it's just because I've never encountered it in my professional life, but I'm a little suspicious of it. Others, please correct my misconceptions if, in fact, they are.
Download Spybot, read the manual carefully, and use it. It's great.
To stop Pop-up ads, Pop-up Stopper Free edition has worked very well for me. It's easy to override if necessary and doesn't get many "false-positives."
Hope this helps