Such a variety of jacket options. My OR Helium lasted, I thought, surprisingly well on a thru-hike in 2011. Fabric is still in fine shape; it's a good idea to reapply the DWR after a lot of use if you want to retain a decent percentage of "waterproofness". If you're talking hydrostatic head details, I'm sure there are better choices, but it served me as well as I think much else would have in wind driven rain and snow, hailstorms, etc.
However, the zipper got wonky after my trip was over. I worked on the zipper, just could never get it to close reliably again. I finally contacted them yesterday and they (Outdoor Research) are replacing this "retails for $150" jacket for free under what they called something like their "infinity guarantee" program. I just clean and ship the jacket to them, which I'll do today, and they're sending me a brand new OR Helium II for free --- I just pay for shipping my old jacket back to them. The only possible downside is that the color choices available just now don't include the ones I would prefer. Oh well! (function over fashion)
So, while I wish they sold these with somewhat more durable zippers, I did hike for months in this and on a tough trail. It's lighter than the other options I think that have been mentioned on this thread, and packs very small.
Just use the zipper with care.