It's sort of a no-brainer really.
-IainB
In several magazine-comparisons of commercial and free contenders over the last couple of years, MSE seems to be quite a no-brainer, indeed..., in this case meaning 'without a proper brain'

Hitrate of MSE being 70-75% where the other free solutions all catch 90-95% of stuff to catch. And even the best paid solutions only catch 95-98%, and the worst commercial ones catch well below these free solutions.
Forgot to mention earlier that I used AVG before switching to Avast, but ditched it when it took too much resources from the PC. Boot-time went down from ~5 minutes to ~60 seconds on older WinXP PC's after removing AVG, and up to ~90 seconds after adding Avast

These resources issues seem to be resolved with the current AVG versions, but I still have to re-evaluate AVG.