With major software suite upgrades I actually advise that users follow the accepted best practice for operating systems and un-install the original and install a fresh copy of the suite.
This provides, IMO, a more stable install of the new suite, as is the case with operating systems.
Obviously you have to treat each case on it's merits as the un-install re-install is likely to remove any customizations that have been made, (though not in all cases), but this can be a minor inconvenience in the long run.
I also follow this route with smaller applications, normally with a major version change 1.x to 2.x etc