In PR 1.2, Qt will also be installed in /usr, not in its current /opt/qt4-maemo5 ghetto. This means that all Qt 4.6 applications should be rebuild once PR 1.2 comes out (which is a good idea anyway).
A note on Qt 4.5 compatibility The 4.5 version of Qt that is currently available for Maemo 5 is a community port that is not supported by us. All the core Qt APIs are of course source and binary compatible also on Maemo 5. However, the community extensions done to Qt 4.5 are not, so minor changes might be in order.
They're maemo and MeeGo... "Meamo!" sounds like what Zorro would say to catherine zeta jones... after she slaps him for looking at her dirtily...