A new Ubuntu with MATE as the default desktop environment is in the making for a few weeks and it looks that the developers are making good progress.
Ubuntu has quite a few flavors under its belt, but there are still a few ones missing, like MATE for example. A few developers, including one from Canonical, are working to make Ubuntu MATE Remix a reality and so far they have done a great job.
MATE is a desktop environment aimed at users who really enjoyed the old GNOME 2, but who also want something different from what everyone else is doing. Most of the major desktop environments are going through big changes, like GNOME and KDE, but the MATE developers are working to keep things the way they were.
Installing MATE in Ubuntu is not enough to properly experience it and the Ubuntu MATE Remix devs have already made a few small, but important modifications that should set their distro apart from the rest.
As expected, the Linux community has some mixed feeling about this, but most people seem to welcome the decision to release a MATE flavor.
From what the developers have shown us until now, it looks like Ubuntu MATE Remix works fine in Virtualbox. We can only hope that the upcoming 14.10 branch will also see a MATE release.