I'm thinking about giving the development version with the upstream keepalive over http 1.1 a try.

Are people using that version in production? Is there a release schedule/estimate anywhere that indicates when that feature might trickle over to stable?

We're using nginx heavily in a pretty vanilla load balancer role - upstream of apache servers, ssl termination in nginx, that's it in terms of features we are using.

It's worked fantastically well overall, we're just flirting with an ephemeral port limit on a few of our sites (have worked around by setting up multiple A records pointed at multiple nginx pairs). If we could get keepalive connections between nginx and the upstream apaches I believe we would be in very good shape and could keep our configuration simple moving forward.