Not the OP, but I'm guessing Ubuntu? Especially since Unity is touch friendly and Ubuntu is generally the best Linux distro out there when it comes to drivers etc. Also because Ubuntu are developing a touch version for the N7.
I'm guessing the battery life is probably around 7 hours or so. Again, take this with a grain of salt :)
Ubuntu Touch is currently in a weird state with regard to Nexus 7 support in that the current pre-release build doesn't support the newer, far superior Nexus 7 2013 model (razor), only the older model (grouper), but Canonical also has announced that moving forward grouper support will be killed and only razor will be supported.
Considering it is all in a developer preview state at this point, this isn't a big deal but may be important information for anyone thinking about buying a nexus 7 right now to be used as a native Ubuntu device.
> Ubuntu is generally the best Linux distro out there when it comes to drivers etc
Thank you for this comment. It shows how RMS was correct; when people think "Linux", they should really be thinking about the kernel inside the computer. This is what handles "drivers, etc" that you were talking about. a Linux Distribution (normally referred to as GNU/Linux, because it has a full GNU system alongside the kernel) can have a branding such as Red Hat, Debian, or Ubuntu. A similar situation exists in the BSD landscape as well; FreeBSD and Apple's MacOS share kernels (Darwin was based off FBSD's kernel), but you're really just using a branded version of Berkeley Systems Distribution.
Ubuntu provides a GNU/Linux distribution (though they seem to be anti-GNU overall) with the latest stable kernel they can get away with. Any distribution with a kernel of the same version will have the same hardware compatibility with "drivers, etc".
Unity is not the only touch interface. Plasma Active and Enlightenment both have touch interfaces that make Unity pale in comparison.
Ever used plasma on an touch screen? It's terrible. Getting better, sure, but not good in my opinion. Unity is far more consistent and modern in touch usage, IMO.