Ok, so this is just based on first impressions--haven't taken it out for a test drive yet since it blazing hot outside without even a hint of rain BUT I will give you my first impressions and some more data not found in other reviews.
First impression quality is superb. For a jacket that feels like it weighs nothing, I really are impressed with the paclite/nylon materials used in this jacket. I don't own any OR gear (mostly gravitate towards MH, Marmot and Arteryx) but OR seems to be top notch quality. I also looked at the OR Foray jacket which was also paclite but full featured and ended up with the Zealot because I liked the fit and lightness better than the Foray. Can't speak to windproofness or waterproofness but others have in their reviews.
Speaking of fit, I am 6'1" and weigh 175 and bought a medium. It is about 31" in the rear (it is longer in the back) and about 28" in the front. I have tried it over my Marmot Superhero softshell and it feels perfect.
All in all, so far I am very impressed. I have done a lot of research via user and trade reviews and the jacket has about 90% positive feedback. The biggest complaints I have seen is lack of features (not the jacket's fault--it is a minimalist product) and waterproofness is sometimes mentioned as an issue. I will use it for a season and comment on that once I have experience with it.