Unity 8 and Mir are currently used on Ubuntu phones, but Unity 8 is far from ready for desktop PCs. Ubuntu developers are currently discussing getting Unity 8 ready to be the default desktop as part of the Ubuntu Online Summit.
Want to stay up to date on Linux, BSD, Chrome OS, and the rest of the World Beyond Windows Bookmark the World Beyond Windows column page or follow our RSS feed.
Unity 8 isn't ready to be anyone's desktop yet
You're free to try Unity 8 yourself on a desktop PC today if the idea of using very early pre-release software doesn't scare you off. Download the Ubuntu Desktop Next images and boot it up on a PC or (recommended) in a virtual machine. You'll see that it still refers to "swiping" and phones in many places throughout its interface.
Unity 8 is still in rough shape on desktop PCs, which is surprising considering it was originally supposed to be the default desktop several releases of Ubuntu ago. Currently, it doesn't have support for existing Linux desktop applications, so it only runs the apps written for the "Ubuntu SDK"--the apps you'll find on an Ubuntu phone. No Canonical developers are yet using Unity 8 on their desktops full-time, which isn't surprising given these limitations.
The proprietary Nvidia and AMD graphics drivers haven't yet been released for Ubuntu's Mir display server, either. Only open-source graphics drivers will function with Mir. Other Linux distributions are moving to the Wayland display server instead of Mir, which probably isn't helping matters. But Canonical is working with Nvidia and AMD to get those drivers out there.
Ubuntu 16.04 will offer Unity 8 and Unity 7 options
Canonical needs Unity 8 to work better as a desktop interface to enable its vision of a converged device future. And it'll have to happen soon--a Ubuntu phone with smartphone-PC convergence features is apparently coming this year.
Developers are working on getting old "legacy X apps" working under Mir. This means all those existing applications on your Linux desktop today, which run under the X.org server. These applications will run in an LXD-based container system and communicate with XMir, a compatibility system for the new Mir display server that allows it to run X11 applications. Canonical wants to create a simple graphical interface for installing these applications and managing these apps, and it'll hopefully arrive by Ubuntu 15.10, which releases in October.
Drag-and-drop and copy-and-paste may not be working by Ubuntu 15.10. Security is a concern here. Like the GNOME desktop's sandboxed applications project, Mir runs applications in isolated environments for security reasons.
Unity 8 still won't be the default in Ubuntu 15.10 though. When Ubuntu 16.04 LTS arrives next April, there will likely be two "stable" system images to choose from: One with Unity 7 and the old X.org server, and one with Unity 8 and the new Mir server.
With a lot of work, Unity 8 could be ready to provide a solid convergence experience on an Ubuntu phone later this year. But average Ubuntu users won't be using Unity 8 until at least Ubuntu 16.04 a year from now. It's also unclear how many users will opt for the new Unity 8 desktop and how many will stick with the tried-and-true Unity 7 desktop.
Simply put, Unity 8 still needs a lot of work.