I wear a PS in Coldwater Creek sizing, but a PM in other stores such as J.C. Penney and Kohl's. That said, I can tell you that most of their tops are shapeless and do run big. I only buy the few and far between tops they sell that are actually fitted and skim my figure. In dresses, I wear a size 8P, but sometimes a 6P, depending on fit. This is true of J.C. Penney as well.
I can sometimes wear a regular size S top in Coldwater Creek; it all depends on how the top is cut and how long it is. It's tricky.
I have never been able to find Coldwater Creek jackets/blazers or pants that fit me. Skirts are easy: always a PS.
Keep in mind, however, that Coldwater Creek has recently changed their sizing. I haven't ordered from them since they did that, as I'm no longer sure their clothing will fit me. I've always been annoyingly between a size 6 and a size 8. When retailers offer size 4-6 as small and size 8-10 as medium, I'm stuck and don't order from them. The size 4-6 is almost always too small, while the size 8-10 is too big.
For me, it's all about finding clothing to fit me in bust and hips without hiding my small waist. Boxy tops are out, which is mostly what Coldwater Creek sells. In general, Coldwater Creek clothing is not cut for my body type.
Hope this helps.