I, myself, have used Ubuntu for my computers running alongside Windows. I have ran Ubuntu in dual-boot and in a virtual machine for different purposes. I haven't been able to use it as my one and only operating system because I use lots of Windows applications that cannot be run on a Linux environment easily. Many have enjoyed the open source OS and it has paved the way for other OSes like Google's own Android as well as Apple's iOS.
Earlier, hackers had made available a way to install Ubuntu onto rooted Android devices like the HTC Evo 4G but this new method will come from the people behind Ubuntu officially.
The release is coming along with no official release date except coming sometime in 2013.
According to many sources, you will be able to use the entire Ubuntu environment on your phone as well as connect it to an external source like a HDMI compatible TV and use it as a full on computer.
You can read more by visiting Ubuntu's website and reading here.