To be honest I haven't tried the docker run stuff yet and still use VMs. It does take time to provision (for me like 30 seconds). I also don't do much serverless stuff (as mentioned in other comments) so my opinion is pretty crappy at best :) .
I wasn't sure how fast Hyper was when I commented but I suppose it is fast (I missed the 5 second subline twice).
One of the big issues to why we don't use Docker is that making Docker images is really slow for us! So while we would get fast deployment/provisioning we would have to pay for it in longer build times. I'm curious how others speed up Docker image building?
What underlying filesystem does Hyper use?
I ask because, on Triton, cloning a ZFS dataset should be very fast, because it is a zero copy operation. It basically consists of copying the metadata for the data set attributes and root directory. So in principle, Triton could perform competitively.
We tried Joyent Triton, which is almost identical to Hyper, but among other big problems it took a LONG time to launch containers. Minutes.