Planning a stage of upgrades for several customers over the next few months....

Has anyone done any of these? What problems did you get, if any? How did you do it? In-place upgrade, new server or a 'link' server to move exchange first?

Can't seem to find any documentation on upgrading SBS, but did find a document on upgrading just plain old 2000 to 2003.

Any tips will be most appreciated.