I'm not sure if you were referring to me, or if PK-Girl is also named Jen, haha...we Jen's are a dime a dozen.
But my KSO Treks are wonderfully flexible. I can roll them into a tube starting at the toe and rolling in either direction, or I can grab one edge and roll them into a tube longways. It's amazing how well you can feel the surfaces underneath them--I can not only feel every curve of a rail, but I can tell whether I'm standing on concrete or grass.
Of course, the trade of is having zero support. I look at my VFF's as "gloves" for my feet rather than shoes. They protect me from stickers and heat, the rubber soles absorb just a touch of impact, and until they're completely worn down, they've got great grip.
I prefer not to wear shoes, just in general, so for me VFF's are the ultimate shoe, just about the only ones I wear anymore, training or not. But people who are used to shoes--and especially those who rely on them for support or to cover little errors in form--are probably not going to like VFF's.