I was a big fan of Avast! Free, and recommended it wholeheartedly, until an update about two weeks ago - when avastsvc.exe suddenly started consuming 85%-100% CPU and couldn't be stopped, even if I temporarily "disabled protection". I put up with it for a day or so, but gave up and went with AVG's free offering (which I had ditched in favor of Avast a couple of years ago when their IDS component became too intrusive, even when disabled.) The day after I made my own switch, I received multiple calls from people to whom I'd recommended Avast, complaining of sudden slowness; I'm pretty sure it wasn't just me.
No company in this sector seems to be able to long resist feature creep and the temptation to monopolize your PC; it's nice to hear from the author that McAfee has apparently got better than it used to be, but it burned through all of my goodwill years ago.