I have a lot of trouble finding a flat casual summer shoe because I usually need a good solid arch.  I bought a pair of Acorn fashion sneakers earlier in the season and I love them. They have enough of an arch and cushioned flatbed that I am comfortable walking in them through a normal day's activities.  I saw this paid of slipons on a great sale, so thought I'd try them.  I ordered a 1/2 size up because my feet do swell in the summer. I wore them all day the first day I got them and they are super.  I couldn't walk for miles in them, I admit, but a normal day's activities later, and my feet and knees were fine.  I've added Acorn to my very short list of favorite, comfortable and pain-free shoes.