Prior to the release of MSE ran net naked for years. No problems. I would occasionally download avast, AVG, or some other freebie and do some scans. Nothing. Hated leaving them installed because they seemed to be more trouble than they were worth.
Gave MSE a shot in 2010 and like it because it's thin and unobtrusive. Fast forward three years and the landscape has changed again. MSE no longer seems to be wise. Based upon the new knowledge I've gained from this post and some comparative validation from other sites I think I will give Kasperski a trial run. If its as good as the ratings suggest I might go ahead and pay up.