I am right on the borderline size wise. I am 5 ft 7 inches and 160 pounds -do i want a medium or large?

I'd go with the large. I'm the same height and just a little less weight, and the large fits great. It does have some extra space in it, for extra layers. It cinches at the waist, so you can always pull it smaller when wearing less underneath.

I suggest the Large for you. I am Ht 5ft 5in, 170#, with much of my extra weight at my tummy. I prefer looser fitting jackets (not huge, just not slim cut), and I avoid princess seams like the plague. This is a lady cut jacket but no so much as if it had princess seams (it doesn't), and it is sized to wear a fleece too. (In my case this assumes the fleece-space is not taken up by the extra 25-30# of spare tummy. If this is how you are built, size up.) My women's XL fits me nicely with a long sleeved T-shirt, and it is an adequately loose, comfortable fit. When I add a fleece the Precip Just fits and it feels a tiny bit snug especially in the slender cut sleeves, but I am still comfy (and I have low tolerance for 'snug'). The sleeves are plenty long and move without 'grabbing', but they are slender. Fine for any weather except hot weather. On hot rainy days with just walking the pit zips prevent heat build up fairly well, but it still gets quite clammy in there. The fabric sticks to my bare skin. With a long sleeved T-shirt the jacket is great. The jacket is unlined except for the mesh fabric on the interior that comprises the jacket's HUGE pockets. I found the mesh a bit hard to manage. I would buy it again, but not for hot, humid climate wear.