Having gotten snowed on during climbs a lot this spring, I decided to look at the Outdoor Research Helium II as a super light storm shell that I can toss in the bottom of my pack 'just in case'.
Basically, it's a great jacket (love the hood), but the body is annoyingly short which makes it staying put under a harness a problem.
I find it best as a backup summer rain jacket. Always keep it in my daily bag for work/around town because Germany isn't exactly the dryest place. For climbing, the same goes. For winter or heavier rain I like the Arc'teryx ALpha FL. A bit heavier yet, but still light and its cut long with little foam inserts on the bottom sides to prevent it from riding up above your harness.