I just commited an update to the Gdb Qt pretty printers, they work now for Qt 4.6. (I didn't test 4.5, but most won't work anymore I guess)
The printers need to poke around in private members, that's why they depend on a specific Qt version.
They are still located in the kdevelop git, instructions on how to enable them see here. (the svn url changed as kdevelop is now in extragear)
Unfortunately my merge request for Qt that would add them directly to Qt got rejected, so it is a bit difficult to support multiple Qt versions - for now 4.6 only is supported. Perhaps in future more people will discover this feature in Gdb and they will get added... You know where to find them.