I'm guessing the battery life is probably around 7 hours or so. Again, take this with a grain of salt :)
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.
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.