I tried these on in the store first.  My usual size seven did not slip off my foot, but as others have said, the too box was a tad narrow and my toes would rub a little on the side.  I'm sure after wearing them all day that that rubbing would hurt a lot.  Plus with foot swelling it would get worse.  So, I bought a 1/2 size larger  (which I normally do anyway) so I could put in a big comfy gel insert.  That insert then made the shoe feel like it was the smaller size again, while making it extra extra comfy to walk on.<br /><br />Here's what I think about Memory Foam.  It appears to be super soft upon first touch, but like all memory foam, as you warm it with body heat, it compresses until it feels like you're walking on  wood.  So I certainly am glad to put a gel insert on top of it.  As well, others have complained that the memory foam is hot (which it is known for that) AND they complain your sweating feet will make it stink.  I imagine thats true as Memory Foam is full of millions of microscopic pores and they will trap bacteria and smell.  You also are instructed never to wash memory foam because water gets trapped in the pores and grows bacteria and mold.  So...cover up that memory foam with an insert.