Bodhi Linux is a Debian based distribution using the Enlightenment Window Manager. They have taken the effort to make a Nexus 7 image (ARM HF), and have gone for the very simple approach seen by the Ubuntu folks: Simply flash the boot and userdata partitions, and you're ready to go.
The images can be found here. (Notice, there are actually two different kinds; boot and root, with different versions of the later). After unpacking, it boils down to:
sudo fastboot erase boot
sudo fastboot erase userdata
sudo fastboot flash boot boot.img
sudo fastboot flash userdata rootfs.img
sudo fastboot reboot
With the Enlightenment WM, they have actually managed to come further towards a UI which suits a small touch screen (compared to the Ubuntu and KDE Plasma Active UIs). The top panel features large buttons, and overall the interaction feels snappy. Now, they have of course not managed to cover all the upstream applications, which is now the next frontier for all of these distributions.
As it is Debian based, is uses the the Debian repositories, and just like the Ubuntu ones, a lot of applications have already been cross-compiled to ARM HF (Hard Floating point). As a crude test, Eclipse-JDT installed and started up fine, While Libreoffice-Writer was missing a package. glxgears installs, but does not start; possibly a driver issue. USB OTG with a hub, keyboard and mouse works out of the box.
So far, this is the best alternative GNU/Linux based distribution for Nexus 7 I've tested. However, as mentioned before, these are still early days, and there will be a lot of work for both upstream application maintainers and distributions to create a great UI experience suited for a touch screen.