14 DAY TRIAL // Ubuntu developers are working to bring the new Unity 8 to the desktop flavor of the distribution and it will take a while, but users are not really mentally prepared for the change. It will be different from Unity 7, which is the version currently in use, and not many people will be happy.
The desktop version of Unity 8 is for now just an oversized tablet and the devs have yet to decide on a proper implementation of the desktop. That means that if you try to run Ubuntu Next, the distro with the default Unity 8 desktop, it will have little in common with the desktop design of future editions.
For now, the Ubuntu devs are focused on the phone version and it will stay that way for a couple more months. It's very likely that Ubuntu 15.04 won't see any major improvements on the Unity 8 front, but that was to be expected. The plan right now is to have the Unity 8 desktop ready to be default in Ubuntu 16.04 LTS.
Unity 8 is a completely different experience
As it stands right now, Unity 8 is available on Ubuntu Touch, which is the version for mobile devices (phone and tablet). Also, the Mir display server is being used and the two pieces of software are closely linked. It means that we won't really have a fully-functional Unity 8 until Mir is ready to take over on the desktop. It's close, but not quite there yet.
The problem is that, unlike previous versions of Ubuntu that got Unity updates, neither really stood out. All the changes were incremental and everything was done with baby steps. The design jump that is coming right now to the desktop is much bigger. It could be compared with the switch from GNOME 2 to Unity, but it's not going to be that dramatic.
Basically, people who have been using Unity until now will either love the new desktop (which will use some of the design principles from the mobile device) or they will hate it, but that happens whenever important things are being modified in a distribution.
The Ubuntu devs have yet to decide on the desktop form for Unity 8, but it's going to share the same codebase with the phone, so there will be some similar features. The upcoming Ubuntu Online Summit that will take place between 12-14 November 2014 might clear some things regarding the desktop edition of Ubuntu. One thing is certain: the Ubuntu desktop is heading towards a major redesign and we can only hope that we'll get to play with the new environment soon.