The recommendation is to use the official Qt 4.6 port. By doing this you are in the safe path for Fremantle, Harmattan and cross-platform development.

The short term disadvantage is that currently there some things missing and rough edges. But precisely by having real projects using these development files you can provide feedback to the Qt team, file bugs to them directly and influence the feature set, priorities, frequency of releases...

See the How to Provide Feedback Section at http://qt.nokia.com/developer/qt-for-maemo-developers . Your very technical and specific questions about the current and future versions of Qt 4.6 for Maemo are welcome there, where the Qt developers are following and active.