after upgrading from Ubuntu 10.04 (lucid lynx) to Ubuntu 12.04 (precise pangolin) almost everything works fine, except: launcher and head-up display.
Launcher problem: left-click on an icon in the launcher sometimes works, but frequently does not trigger start of the application in question. Luckily, starting the dash works reliably, so I can always start my applications via the dash. Nevertheless: the launcher should work.
Head-up display does not produce any search results.
My hardware: Toshiba Satego X200 laptop.
Prio to upgrading I tested Ubuntu 12.04 from a bootable DVD and it worked fine. Prior to upgrading I de-installed almost all non-Canonical-supported packages, and afterwards re-installed via Ubuntu Software Center and Synaptic whatever I need.