There was a very interesting session at UDS by Google developer Thomas Bushnell. He talked about how Ubuntu, its derivatives and Goobuntu (Google's customized Ubuntu based distro) are used by Google developers.
He starts by saying 'Precise Rocks' and that many Google employees use Ubuntu including managers, software engineers, translators, people who wrote original Unix, people who have no clue about Unix etc. Many developers working on Chrome and Android use Ubuntu and his cook in Google office uses Kubuntu.
Goobuntu is Google's version of Ubuntu and it is based on LTS releases. They make no changes to default UI of Ubuntu like Mint but they do use their own security authentication system and a internal repository system like Launchpad. They like that Ubuntu does a great job of a desktop that works out of the box.
Also many Ubuntu default apps like Ubuntu One are purged from systems as their work information can be sensitive and they also can't send core dumps.
Upgrading to Ubuntu 12.04
Ubuntu systems at Google are upgraded every LTS release. The entire process of upgrading can take as much as 4 months and it is also quite expensive as one reboot or a small change can cost them as much as 1 million dollars.
This time, however, Ubuntu 10.04 LTS workstations at Google won't be upgraded to Precise until next year.
Google employees love to use KDE systems and they will be really happy when their systems are upgraded to Precise as lots of great work has been done on KDE since Lucid was released. However, not many employees like new UI changes meant for consumers and not developers. Some of the Google employees also requested removing Unity and Gnome 3 and using xmonad instead.
Lastly he said that 2 years for an LTS release is quite reasonable and gives them enough time prepare things.
Full video of Google's presentation: