For starters, I'm tough on my cross trainers. I practice Krav maga in a gym that also does a lot of crossfit type cardio classes both indoors and outdoors. I spend a good 8-10 hours a week at my gym, so my shoes are worked hard!<br /><br />When new, these shoes are incredibly comfortable. The toe box on the Nike Flex TR shoes tends to be a bit wider than the average shoe which I can appreciate because many cross trainers tend to be narrow. My biggest gripe with these shoes is the sole. There's so little grip and it wears quickly. If you look at the pictures, the black portions of the sole are your traditional grippy rubber and the white portions are a soft slick foam like material (most of the sole!) So far I've had 2 pairs of shoes in the the flex series and this has been the case for both. I've purchased 2 pairs because they are very comfortable and the aforementioned generous toe box.