I returned a lesser grade of P.I. bibs because of fit and quality issues, but was really intrigued with the In-R-Cool material because I live and ride in a very hot climate with very intense sun. Realcyclist was great about taking back the other bibs and I ordered the PRO.
I am blown away with the fit and quality of the PRO bibs, and I am super impressed with the ability of the material to reflect heat. The geniuses at P.I. have hit a home run, as I can feel a very noticeable reduced amount transferred heat in direct sun. The chamois is very comfortable even at the end of long rides, and the upper fits well without being too tight or digging in to the shoulders. I am 5'9", 160 lbs., and the medium fit perfectly.
I have a number of different brand bibs, but these are the best I own and are better than much more expensive ones I own. I will definitely be getting additional pairs of these.