I always re-install - I found Ubuntus upgrade to be less than satisfactory. Has been for years. The way I manage it is to have /home on a separate partition - then upgrade using the same username/password. Eveything "just works" - applies even if you need to go back a (*one*) release.
To manage the packages, try "aptitude search '(~i !~M )' > myPackages" on each system (before and after). Still need to manually compare.