Those of you who followed the development of QMC2 0.1 will probably continue to use the SVN revisions of the 0.2 series, whose development has just been started.
Be aware though that some of the new design goals have impact on the requirements: Qt 4.2 will no longer be supported, Qt 4.3+ is needed now! And as it has already been planned for a while, XMAME support has now been dropped – the project is inactive since MAME 0.106 and no one appears to be still using it, so it’s no longer worth the hassle.
See the current todo-list from SVN for more information.
The QMC2 dev-team