From what I can tell from the 2 recent upgrades, all sort of problems occurs: rootfs, reboot loop, themes, memory, asking to use NSU, operation failed etc. due to people having apps from evil repos and custom hacks/mods. The upgrade itself is never perfect for most of us.

Those with the N900, who wouldn't want to try out stuff from the evil repos?
Does Nokia expect us just to use the ~200 apps available? If yes then Nokia is mistaken.

We want to hack/mod our phones the way we want and this will surely cause an issue when upgrading firmware.

So perhaps spending ages to perfecting the upgrade process is a waste of time? ie needing to go to 2009.44 before we can upgrade to PR1.1