I'm not sure why people are having so many issues with sizing. They tell you that they vanity size by about 2", and to make sure you get it, you can check measurements of waist, thigh, rise, etc on their site.
well as I stated, I did go by their sizing chart (agonized over it actually) and the pants I received were at least an inch big on me.
It may have something to do with the higher back (ass crack cover) causing the measurements to be different from where they actually sit on your waist.
Next time I think I'd go with a 31 which is on the chart as 33" even though my waist measures 35".