Qt 4.7 beta 1 is now available in the qting-edge overlay.
To install it, add the overlay (using layman or PORTDIR_OVERLAY) and unmask qt-4.7_beta1 by copying or linking the keywords file we provide in your /etc/portage/package.unmask/ folder.
ln -s /path/to/qting-edge/Documentation/package.keywords/qt-4.7 /etc/portage/package.unmask/
# IF YOU USE A package.unmask FILE, run the following INSTEAD
cat /path/to/qting-edge/Documentation/package.keywords/qt-4.7 >> /etc/portage/package.unmask
then update your world:
emerge -avDuN world
if you only want to update Qt, run
emerge -av1 $(eix -I --only-names x11-libs/qt-)
Please report any ebuild-related bugs you find in our bugzilla, prefixed with [qting-edge] in the summary!
Enjoy 
Any word if this is stable to use with KDE 4.4.x?
Answering myself, it works well using ABI compatibility. Performance and correctness are good.
As an aside, I disabled the forced raster useflag. In my not so humble opinion, this is wrong. You’re using a nasty hack to improve performance on the shoddy Intel graphics drivers/cards at the expense of real GPUs and breaking X11′s strengths in remote usage in the process.