I've got a nice Showers Pass waterproof shell. It's no lightweight, though. Full-length pit zips, back vent, adjustable wrist straps. Works okay up to about 75ºF or so, presuming a proper (wicking) base layer. Have worn it well into the 20's. Have been snowed, sleeted and rained on. It's pretty darned good. Just not a featherweight shell. Though I've only had it a couple years now, it wouldn't surprise me if it remains waterproof for many, many years.

Can't say whether their lighter-weight stuff would be equally waterproof. Worth looking at.