I am a size 7.5 and I got a  M/L, which on the Get Grounded website is listed as 7.5-8.5. Here on Amazon, M/L is listed as 8-9, which may be why so many people feel this shoe runs small. Anyway, I am a 7.5 and the M/L fits me perfectly. That being said, I have very narrow feet. I can see how someone with wider or even average-width feet would find these uncomfortable. I don't think the sizing on these shoes is accurate. I recommend ordering one size larger than what you actually wear.<br /><br />As far as comfort goes, they aren't bad. But they aren't fantastic either. They are quite a bit heavier than any other pair of flip-flops and at first I found them clunky, but after wearing them for an hour or so I got used to them. The part between the toe is quite stiff and I found it a little annoying but not painful. They are not completely flat but if you need a shoe with good arch support, these are not what you're looking for. After wearing them for about 12 hours, my feet felt fine except the part between my toes was a little sore.<br /><br />The worst part for me was that the colour rubbed off all over the bottom of my feet. The groundals site says that this is to be expected when the shoes are new if you tend to sweat a lot or wear lotion on your feet. I did neither of those things, yet the soles of my feet looked like they were covered in ink. Even after scrubbing them in the shower I could not remove the stains entirely. I included a picture of my foot before showering.<br /><br />I'm giving these a 3 because I love the concept of a grounding shoe, but this design needs to be tweaked. I will keep wearing these until I find an alternative.