It sounds like they are just building on cgroups etc, which are already part of the Linux kernel.

I would argue that virtual machines at a hypervisor/hardware level were just a hack for OSs not living up to their isolation promises/obligations. Strong OS level isolation implementations (cgroups, namespaces etc) allow people to put isolation back where it belongs, the OS.

The job of the OS is to control the hardware, wrapping the OS is software to emulate hardware is ridiculous and VMs generally have much more performance overhead than isolation containers.

Containers have existed as long as virtual machines have. FreeBSD implemented "Jails" back in the late 90s / yr2000. Linux also has OpenVZ and Solaris has Zones.

If you couple a container with a CoW file system that supports snapshotting (eg ZFS or BtrFS), then you can have most of the features you'd expect from virtualisation but without as heavy footprint.

Containers are an underrated and often forgotten solution in my opinion.

lxc leverages hvm I think... someone correct me?

edit: it's too early, sorry this has nothing to do with your post... but I hope someone does correct me about hvm.