hard coded to some local qt libs on Mac OS X 10.8.2
I tried the latest beta under my machine (with local Qt version 4.7 installed) from sigtrap get the following as an error upon launch:
Dyld Error Message:
Library not loaded: /usr/local/Cellar/qt/4.8.2/lib/QtGui.framework/Versions/4/QtGui
Referenced from: /Applications/Sigil.app/Contents/Frameworks/QtSvg.framework/Versions/4/QtSvg
Reason: Incompatible library version: QtSvg requires version 4.8.0 or later, but QtGui provides version 4.7.0
So it appears I either need to update to my own 4.8.2 version of Qt or the build did itself is linked to qt libs not part of the Sigil.app framework.
Hope this helps,