Well i just installed the beta avaialble via www.microsoft.com im impressed its a product i knew microsoft would release a anti spyware program, it looks very good ill report back after a few days of use!
The interface is very nice, as usual. There are 2 options. 1.) Intellegent scan (quick scan) 2.) Full computer scan
I tried a quick scan and when the scan finished (took about 1:30 mins), but then it froze(it's beta release, so duh). But I got it cleared, and it turns out that I had 13 infections, so I cleared that (was very fast and clean). So far, MS Anti-Spyware is a very good start. I would give it a A-/B+ grade.