I'd like it to be more like git. Yes Docker has "push" and "pull", but I want branches, and automatic attach when I do a checkout, and rollback when I screw it up.
As a developer I'd like to be able to check out a docker image, work _in_ it, and merge it to master when I'm done. When my code is deployed, I'll know _exactly_ what is running.
Managing secrets and environments (so the container knows when it is in production instead of running on a developer's laptop) is important to get this to work well.
It feels like it is half way there already. I'm looking forward to when it is as straightforward as git for a developer to use. I'm not too worried about start up time - the biggest drawback to slow startup time is when you are running very sensitive autoscaling that is tearing down and spinning up new nodes very quickly. If you have that problem you may want to rethink your node size, hysteresis, and scaling thresholds.