I have a medium Twin Six and 2 medium Terry jerseys, which all fit me very well. PI is all over the place- 2 that fit great, 2 that are really too tight in the bust, some of the fitted ones I can't even get on, and one I tried on that was way too big. The large size in the fitted styles are proportioned wrong for me.
I'm short with a short waist and relatively generous bustline.

Shorts seem to be more consistent- size small works for me right now in Giordana, PI and Performance. I have one medium in Shebeest that doesn't seem too large. I hate the grippers on the Performance (Ultra)! I don't even notice the gripper on the Giordana shorts.