You can download this daily build of Ubuntu from Softpedia
Canonical has just released a new Ubuntu 14.10 image that only comes with the new Unity 8 as the default desktop environment, but don't expect it to become one of the main releases in October.The Ubuntu developers have been working on the new Unity 8 desktop environment for some time. It's already implemented in the Ubuntu for phones version, but it will take them a while to get it to work on the desktop.
There are several hurdles that need to be overcome in order to make the transition from a mobile platform to the desktop. Sure enough, the desktop environment is important, but there are a number of other things that need to be considered.
For example, Unity 8 runs on Mir and not on the X server. This is no longer a problem on mobiles and it looks like things have settled down. The display server Mir is working just fine and a lot of bugs have been squashed. It may not be ready for the desktop, but it doesn't mean that Ubuntu developers are not doing everything they can to make it happen.
The new daily image provided by Canonical is still using Xorg, which is required, for now, by a number of packages. This is not something that can be used, at least not yet. Users won't be able get past the login screen, but fixes are incoming.
The new version of Ubuntu 14.10 might not even work on some hardware configurations and there is no indication that it will be able to run without any issues in virtual machines. The release date for the next Ubuntu is October 23, but it's unlikely that Unity 8 will be ready until then.
Mark Shuttleworth, the founder of Canonical, said that, in fact, Ubuntu users won't see much of a difference from the current Unity 7, with the exception of a few components that will change. Most of the desktop experience will remain the same.
This release is aimed more at developers, but it's good to see that its makers are letting users play a little with the next Unity without having to install all the packages in their pristine Ubuntu 14.04 LTS desktop.
If you manage to start the new operating system, you will be prompted with the login screen. The username is "ubuntu-desktop-next," without the quotation marks, and there is no password, just hit enter.
You can download Ubuntu 14.10 with Unity 8 from Softpedia, and keep in mind that this is a daily build, which means that it's updated on a regular basis.