Here's more followup on my VFFs.
I started running in my VFFs (Classic version) at the end of June. I stupidly didn't take it easy - just did my usual 5k run like normal. That caused a fair bit of blistering, and the front pads of my feet felt pretty abused. But the running part of it was great - my feet felt really light (duh), and generally it felt more fun.
I kept doing it, just building up more blisters/callouses, and finally ordered some Injinji toe socks to go with the VFFs. That eliminated the blister problem completely. I still haven't gone more than 4 miles in them {embarrassing to post that in the ultra forum!!
}, but I'm sold (I typically run 5k 3 or 4 times a week, so my mileage is currently pretty low, but I'm about to start ramping that up for a half).
A big change I have noticed is that when running with my ASICS (forgot what model), which were properly fitted at a local running shop, I would have some knee discomfort after running, and occasionally sore hips. I haven't had any soreness whatsoever in knees or hips since running in VFFs. My feet do feel a bit "worked" after runs - but this is akin to the feeling in your hands after using hand tools all day, not anything pathological.
I have also tried two other models of VFF - I tried the KSOs, and the Sprints. The KSOs didn't fit - the fabric on top of my foot felt way too tight and uncomfortable, following the fitment guide online (and bigger would result in toe beds that are too long). The Sprint model has a funky heel compared to the Classics - the vertical piece is less substantial, and there's a whole lot of strappy action back there. I'm going to send them back and just go with another pair of Classics... I've never had any trouble with the Classics falling off (but I don't really use them in the water).
For what it's worth - the VFFs seem damn near indestructible - I've had them for 3 years, taken them on hikes in the Sierra, go running in them, and have even (stupidly) put out a fire with them. The sole was undamaged (it's Vibram), but it still got hot as hell on my feet! They also did get some serious stink when worn often without socks, but the washing machine took care of that, and with the socks, they don't reek anyway. Newer models allegedly have some antimicrobial junk going on.
Oh - and I'm down to 9:00/mile and still dropping. 
So, yep, I love 'em!