Absolutely love these. Fit is pretty true to size length wise, with a slightly wider than average toe box. I have a wide foot. This toe box was just a little too narrow in my size, so I went one size up. Usually a US Mens 8, so I ordered Mens 9. The 9s fit well and had space to fix in some orthotic inserts. They come totally flat inside with a small amount of squish (which is slightly better than typical shoes).
Rated 0 on a scale of minus 2 to 2, where minus 2 is Runs Small, 0 is True to Size and 2 is Runs Big