[e12e]

Marketing, maturity, support and tooling?

I think the only ones that really ran with KVM were/are Joyent with their Smart OS - combining (some of the) tooling/tech that makes Solaris Zones great with a Free and Open operating system, freedom from Sun/Oracle and support for many guest platforms (and/or low overhead "native" zones).

I think the only real downside of Smart OS is the same as with Open Solaris (or pretty much any other "it isn't Linux"-unix-like OS'): drivers and hw support.

The great thing with Linux as a host, is that (edge cases excepted) you can literally run in on your entire infrastructure (right now, or in the near probable future) -- from phones and tablets via desktops and laptops through servers, clusters and pretty much anything beyond.

I'm sure we'll see some backlashes from the new monoculture, but I think overall it's a bright future.

And we can have our occasional parties arguing for why everyone should really use (Dragonfly|Free|Open)BSD/(Open)Solaris/Plan9 because it has X, does Y better and has more consistent and better documentation.