I've been running on and off for about 3 years and have always found Nike Air Pegasus to be comfortable.
My normal running distance is 5-10 miles but I have ramped this up twice to run half marathons.
In normal running I have never experienced black toenails and in my first half marathon (2013, wearing well worn in Pegasus 28's, size 8.5) I also had no sign of toe trouble.
In my second half marathon (2014, wearing Pegasus 30's with about 50 miles of use, size 8.5) I ended up with black nails on both big toes.
Terrain for both races was similar but the 2014 event was significantly hotter, I'm curious why I may have ended up with such different results, whether the heat (25c) may have meant that my feet swelled more than usual or something?