I didn't have any trouble going to Keen sandals after wearing the VFFs for a couple weeks pretty much straight, but Keens are well known for their toebox and foot-friendly shape. ANY shoes that squash my toes feel absolutely wrong - even my bike shoes.

I feel like the VFFs are one of those toe aligner dealies that you see in the SkyMall catalog or in the back of magazines. My left pinky toe always feels funny the first time I put it back in the VFFs after wearing other shoes, like it's being put back where it belongs. I wear them for a while, my toes feel great and the shoes go on super easy, then I wear regular shoes, even just for a night, come back to the VFFs, and I have to argue with my toes to get in them.