Re: ubuntu and Raspberry Pi
What specifically about Ubuntu do you want the Raspberry Pi to do? As it is, Raspbian is Debian based like Ubuntu, so if you are familiar with Ubuntu, it is easy to find your way around a Raspberry Pi. Since the Pi uses lxde it is similar to Lubuntu. Many applications that are not installed by default are available using apt-get, aptitude, or you can install synaptic. You don't really need Unity, you can just use desktop launchers.
It is not real quick with single core 700 MHz (or whatever you reliably overclock it to). But a nice thing about booting from SD card is that you can totally change its function by switching SD cards. You can have one with Raspbian for doing general thinks or playing around with programming. You can have another with one of several XBMC versions for multimedia (which has some internet TV stations, but will not do things like hulu or netflix). And when someone asked how to boot it into a terminal program, I figured out how to have one boot right into Quake3 (which runs quite good on the Pi). The autologin script I found required the korn shell, but it was simple enough to install ksh. It worked even powering the Pi from the USB port on an HDTV using HDMI for audio/video and using wireless keyboard and mouse (1 Logitech unifying receiver for both).
i5 650 3.2 GHz, 8 GB, nvidia GTX 750 Ti, 32" 1080p | i7-4700MQ, 8 GB, Intel HD 4600/nvidia GTX 765M, 15.6" 1080p | etc.