Our approach is to focus on functionality and correctness first, and then improve performance over time.
We're building up a suite of performance benchmarks to help us track progress-- are there particular benchmarks that you would recommend we add? I'll certainly add "CPU load while idling" to the list.
Just my two cents: I think that the interface and features are excellent and a joy to use, but performance was a show-stopper that forced me to quit using the Beta for Rails-application development:
- a simple request that took ~1/3 of a second using VirtualBox and Docker Machine took six seconds on Docker for Mac - a more complex request went from one second to twelve seconds
I didn't have a chance to dig into it, but I would guess that it has something to do w/ osxfs and the many files that Rails loads, as it reminded me of the difference between using sharing files via VirtualBox's own file sharing vs. NFS, the latter being a significant improvement.
Definitely check out the beta forums as most of the issues I've found have already been reported with workarounds.