Upgraded the OS on Stargate from Ubuntu LTS 6.06.2 to 10.04 LTS (via 8.04.2). Some small quircks needed to get fix - but all in all it took barely 30 Minutes per OS Upgrade, and the fix at the end, a little bit of googling around, to identify that applications have changed API that needed to be adapted.

A real 2 hours for the upgrade processes, and another 2 Hours for the fixes. Try that with windows - as going from Windows 98 through to Windows Xp then to Windows 7 :) Good Luck !