Installed, uninstalled
Ubuntu Phone stayed on my Nexus for almost an hour, I wanted to feel it running on my phone even though I was well-aware it was going to be mostly mockup, similar to what was demoed at CES last month.
On a slightly related note, there was a nice analysis and comparison of upcoming phone OS contenders last week, covering the progress, teams, approaches, and industry support and tips for success for Ubuntu Phone, Tizen, Sailfish OS, Firefox OS, BB10
http://www.brightsideofnews.com/news/2013/2/5/analysis-new-mobile-operating-systems---ubuntu2c-sailfish2c-tizen2c-firefox2c-blackberry.aspx