From: http://labs.trolltech.com/blogs/2009/08/31/qt-46-on-mac-os-106/
"I can confirm the above fix solves the install on Snow Leopard problem - where is hangs/fails when doing “Validating Packages” early in the install. To solve, first time you run installer uncheck the Qt Docs option under Customize - then re-run and install just the docs."
I'm using it on Snow Leopard without problems, Only one word of advice Qt 4.5.2 has a drawing issue on combos and context menus, to fix that you need to patch two files and rebuild Qt. Therefore maybe you can use the source distribution instead of the binary one, and download QtCreator separately.
Regards