make sure you do this first:

apt-get update && apt-get -u upgrade


Just to find out how many packages are held. A regular upgrade won't "uninstall" things. Where as this:

apt-get update && apt-get -u dist-upgrade

Will take you head long into problems if they exist.

Personally, I do the "upgrade" until everything upgrades properly (as in all the gnome packages go in or the huge set of OpenOffice packages go in and then I look at the dist-upgrade to make sure nothing is gonna get removed I want.