Ok, I just ran this program.
Normally, I update and run AdAwareSE & A-Squared every three or four days but at the time I ran Spyware Doctor, I hadn't updated or run either for about a week. I also didn't clear my cache.
It picked up 52 instances of 'malware'.
That's about 30 more than the other two pick up every 3 or 4 days.
And when it had finished, it said I had to register, ie - pay, if I wanted to remove them.
That, to me, is really not very nice. Scare the hell outta some naive person telling them their computer's full of crap and then demand £20.00 to sort the 'problem' out. Hmmph.
On inspection of the scan log I noticed the majority were just tracking cookies, which can be easily removed by just clearing your cache. They're mostly harmless anyway.
What was interesting is that it actually pointed out internet addresses stored in XP's 'My Favourites' as threats, saying it 'may' be a threat to visit that particular site.
Admittedly, some of the links I have are a little naughty 'key generators' and the like, but this, to me, was overeaction and scaremongering on the software author's part.
I then ran AdAware SE, that picked up 21 tracking cookies, and A-Squared, which picked up just the one nasty.
I'd say the program does work but they're selling using scare tactics and 'nannying' the average user.
They will not be getting my £20.00.