Bought a pair for my 25 yr. old son and a pair for my 18 yr. old dtr. He wears his when he is running in and out of the house quickly and is too lazy to put on regular shoes. She has been wearing hers to work where she stands on a hard floor for 4-8 hrs.  Both say they are quite comfortable and that they appreciate the ease with which they go on and off.  He felt his fit fine - bought size 11 and that's what he normally wears.  She felt hers were a tad snug - wears a 9-9.5 and bought a 9.  However, she usually wears hers without the strap in the rear and feels that wearing them has relaxed the fit some.