I think that there may be only one answer to cure this.
Is Mint DE available for ARM? If not, we clearly need to use the Intel z3770... oh, wrong thread.
Seriously though, Ubuntu has sucked and will suck as long as they keep pushing that POS Unity interface. That thing is a continuous train wreck. People have left that distro in droves and are fleeing to Mint.
There are two main Mint streams. One derives from Ubuntu - which derives in turn from Debian. The other Mint derives directly from Debian.
Unfortunately, the Mint DE doesn't get a lot of love. It's a rolling distribution off of Debian Testing. Mint is great, but Mint DE isn't really a prime-time distribution yet.
http://www.linuxmint.com/download_lmde.php
The other Mint stream (Ubuntu based) has multiple versions that vary based on UI.
http://www.linuxmint.com/release.php?id=21
Cinnamon:
http://cinnamon.linuxmint.com/
KDE:
http://blog.linuxmint.com/?p=2508
Mate:
http://mate-desktop.org/gallery/1.6/
Xfce:
http://linuxmint.com/rel_olivia_xfce_whatsnew.php
Compare
http://www.debian.org/ to
http://www.linuxmint.com/ .
One drawback to Debian is that, well, it's hostile to new users to even figure out which version they should download and how to install it.
http://www.debian.org/ isn't the most intuitive site around.
Debian supports the same desktop UI selections as Mint:
https://wiki.debian.org/DesktopEnvironment
However, if you're a novice trying to figure out how to get from 0 to a working system with UI, it's frankly a bit frustrating to get there.
For the Pandora successor, though, that doesn't matter so much as it would come pre-loaded and our community could help write up some device specific instructions on installs & upgrades.
I have tried all 4 primary desktop UI options that are officially supported on Debian (GNOME, KDE, Xfce, LXDE). GNOME is very pretty and has the largest software base focused on it, but is VERY resource intensive. KDE is very Win95 feeling and has kind of fallen out of favor the last few years. Xfce is very good for a light system, but needs packages from GNOME and KDE to fill out. LXDE is highly efficient and 'light', but feels a bit stripped down.
For the Pandora successor, I'd suggest focusing on Debian Stable with Xfce or LXDE for the UI.
Something else to keep in mind... Although there is an ARM repository for Debian, I don't think it gets quite the love & updates that the X86 repositories get. Packages could very well show up on X86 stable before they go into ARM testing.