14 DAY TRIAL // Canonical has a very dedicated team building the Mir display server, and it is updating it on a constant basis. Version 0.0.15 has just been released.
Ubuntu 13.10 will no longer feature the XMir display server as the default boot option, but users will still be able to download and install it from the official repositories.
According to the changelog, running the unit tests is no longer causing an EPERM exception in open_vt because Mir was already the session leader, meta-conflicts are now solved before they create a problem, a typo that broke CI builds has been fixed, and much more.
A complete list of improvements can be found in the official changelog. Download Mir Display Server 0.0.15 right now from Softpedia.
Remember that this is a development version and it should NOT be installed on production machines. It is intended for testing purposes only.