Nginx's development branch is generally considered production ready [1]. I trust the nginx core team not to introduce potentially problematic changes. As an example, the recent spdy integration [2] has lived in a parallel branch for over half a year.

The dev branch is officially upgraded to stable infrequently, maybe once a year.

[1] http://blog.bigdinosaur.org/nginx-dev-or-stable/

[2] http://nginx.org/patches/spdy/

Thanks, that's really helpful! I wouldn't have considered that. It still seems risky using a dev branch for my main web server, but I'll look into it.