And yes derivatives will use Mir/XMir or X.org, whatever Canonical choose. Just because that way user can install "k/l/xbuntu-base" and have kubuntu/lubuntu/xbuntu on normal Ubuntu installation. Messing around with display server will break that compatibility..
I'm very much looking forward to Gnome 3.8. I've stuck with fallback mode not because of crappy graphics hardware but because I have two large monitors and lots of the same app open. Taskbars are the least worst way of dealing with that and finally the Gnome people are combining shell with UI like that.
But being able to run 3.8 is more problematic. Ubuntu now trail releases instead of having fresh versions. Even if you use ppas to get a more recent version, other infrastructure (eg gstreamer) still ends up trailing. I also want to leave Ubuntu - their requirement for CLAs means they want to prevent participating with others as equals, and the NIH syndrome means they don't play with others anyway.
I tried Arch which is up to date, but the self assembly side got far too tedious (not to mention poor documentation). Fedora wouldn't let me pick existing partitions for installation and presumably won't update to Gnome 3.8 until Fedora 19. Debian testing is on Gnome 3.4. Sigh.
The Ubuntu Gnome developers are doing a GREAT job. That benefits gnome as much as ubuntu. So I really hope these people can make ubuntu work with systemd/wayland instead of gnome working with mir/upstart.
But being able to run 3.8 is more problematic. Ubuntu now trail releases instead of having fresh versions. Even if you use ppas to get a more recent version, other infrastructure (eg gstreamer) still ends up trailing.
At the moment Ubuntu 13.04 "Raring Ringtail" has gstreamer1.0 1.0.5-1ubuntu1. The latest version on the GStreamer website is also 1.0.5, released 8th Jan 2013. But I get your point that at times Ubuntu is behind, which could in fact happen if gstreamer 1.0.6 is released before Raring and Ubuntu does not pull in the newer version. In that case the PPA for GStreamer developers is a good option - it currently contains packages of gstreamer1.0 1.0.5-1 for Ubuntu 12.10 "Quantal Quetzal" and Ubuntu 12.04 "Precise Pangolin". It's available under "Other versions of 'gstreamer1.0' in untrusted archives." at the bottom of the page at https://launchpad.net/ubuntu/+source/gstreamer1.0
But I get your point that at times Ubuntu is behind ...
In 12.10 they shipped Gnome 3.4 so the base level of other packages needed to be compatible with that Gnome version even though 3.6 was the current Gnome version. I did of course get Gnome via PPAs. My poorly made point was that once they start holding back on any one component, then chances are they have to start holding back on related others. Before you know whole swathes are held back. You can still update some via PPAs but it can quickly get unmanageable.
This was why I abandoned Gentoo for Ubuntu many years ago (in addition to the unnecessary drama). Newer versions of packages have to be marked as stable, but it kept not happening for various reasons. The simplest one is that marking something as stable took effort and could break something, so inaction was the default. You could go into a file and mark packages as being okay using their "unstable" versions, but my list kept getting longer and longer. They were lagging Gnome releases by over a year. This is still a problem now - with a piece of software I wrote the most recent stable release they have is from 10 months ago, and there have been 6 releases since. I can't even figure out what version of SQLite 3 they consider stable.
I'm also annoyed that Ubuntu is so opposed to systemd. Virtually every other distro has or is in the process of adopting it. The technical merits are very tangible. Why do I have all these daemons running (eg CUPS/printing) even though I haven't used their functionality? The containerization is excellent for servers so you can stop runaway bad behaviour. And the logging while non-traditional is more solid.