Folks are welcome to disagree, but Docker has a history of shipping software which uses a 3rd party feature which breaks, to which they frequently responded "not our code, talk to someone else": btrfs instability, corrupted volumes due to conflicting devmapper libraries, iptables dropping routes, upgrades orphaning containers, etc.
I realize they don't have control over all of the variables, but constantly releasing unstable 3rd party features was not the greatest behavior, and the "Not My Problem" response to issues is aggravating.
All that said, since they're working against their own fork of xhyve, it is a sign that these kinds of issues will be addressed by the Docker team this time, which is a good thing.
Yes, any new virtualization projects should strongly consider using it, but that doesn't mean any issues with projects with have a massive investment in tooling and ecosystem should be considered deprecated and dead just because of this.