Tried it out yesterday
I tried it out on a live DVD yesterday, mainly to see what Unity 8 was like. Unity 8 seems to work fine on my hardware (AMD A8-5600K APU with Radeon(tm) HD Graphics × 4). Some of the effects looked nifty, but I prefer the Unity-7 UI in terms of making my life easy. In particular, I can't imagine living without virtual desktops, and I didn't see any in Unity 8. What is more, if the launcher bar is supposed to pop out somehow, I didn't see it. Instead there was what looked like a "launcher window" I'll call it. However, Unity-8 and Mir are still focused on mobile and tablet targets, and desktop trails after. This is an understandable, as Unity 7 is probably by far the best UI to be found on Linux today, so there's not a lot of pressure to change it. I use 16.04 on a daily basis, and I'm quite content to wait.
I didn't try the Snaps, so I can't really comment on them.
As for the (Gnome) "Software" package, I install command line and library packages using a GUI (Ubuntu Software Centre). It's a lot easier to search for and install packages that way. Using a GUI I don't have to Google a package name to find out the exact package name (which is often not the same as the common name) and what it does, and the integrated ratings system helps as well. "Software" is completely pointless if it can't handle everything. Ubuntu Software Centre handles things by letting you show or hide non-GUI items.
As for Nautilus, the reason that 16.04 shipped an old version is because at the time Gnome was in one of their "let's rip out all useful functionality" phase of "simplifying" things, and the latest version at the time was rubbish. If the pendulum has since swung back to making it useful again, then that's fine. I'll have to boot up the live DVD again and try it out.
I wish they had stuck with the old version of GEdit and Gnome Terminal for 16.04 by the way. The Gnome devs have ripped out the most useful GUI parts of the UI and forced everyone to memorise keyboard short cuts in order to "simplify" the UI to conform to the current Gnome group-think on UI design (which says that the way to make things easy to use is to simply not have any useful features).
As a correction, this is not the first Ubuntu release to not fit on a CD. It is in fact only marginally larger than 16.04, which also did not fit on a CD. What is more, 14.04 did not fit on a CD either (14.04.4 is 1.1GB, 16.04.1 is 1.5GB, 16.10 is 1.6GB). I'm not sure when that restriction was removed, but it was a while ago. The main reason for this was to accommodate more standard applications.
Oh, and as a tip for anyone looking to try out Unity 8 on a live DVD, the way to get to it is to boot up the DVD and then log out (using the gear symbol at the upper right). At the log-in screen, click on the Ubuntu logo beside the user name box, which causes an additional log-in option to appear. Select that, with user name of "ubuntu" and a blank password, and it will log into a Unity-8 screen. Explore the edges of the screen with your mouse to cause features to appear - this is the desktop equivalent to "swiping" the edges on a touch screen. Unity 8 is a mobile UI which has been adapted to the desktop. The interactions are not really "desktop-enough" in my opinion, which is I suspect one reason why they haven't made it standard yet. There are only a couple of applications available, as they have to recompile them to get the standard UI libraries to use Mir instead of X, and they didn't do that for all the apps (since it's just a demo).
All it all, it looks pretty good. I use Ubuntu with Unity 7 (16.04) on a daily basis, and I much prefer it to any other Linux distro or any other version of UI on Ubuntu that I've tried. I also prefer it to any version of MS Windows that I've tried. I don't have enough experience with a Mac to really do a detailed comparison there, although superficially I would say it's at least as good if not better than a Mac from an ease of use standpoint.