I have found these to be incredibly comfortable for both running and general use. As others have noted, there is heel slip but they don't seem to cause blisters. The fit is very comfortable, like slippers, and the sole is sticky (which I really like)
My ONLY gripe is that the sole is totally flat, so I can't use a gaiter unless I cut a groove in the sole. I'd give 4.5 stars if I could.