The upgrade went absolutely flawless for me. There was only one dubious moment: At the almost very end of the upgrade the system started counting upwards very slowly from 0 to 100. This did really take several minutes in my case and the counting number without any further notice was a bit confusing and tempting me to abort the upgrade. But my patience was rewarded with a system which still worked flawlessly after the upgrade.
My GMA500 (Poulsbo) netbook will still have to wait a bit, I want to be sure the graphics work fine -- including VAAPI acceleration -- before I start the upgrade. But of court LTS makes it very attractive then.
It turns out though the backlight control is much prettier, it's also broken and thus much more useless...
But I really like that most customized repositories were automatically re-enabled as lucid variants after the upgrade.