In order of maturity (highly subjective): gtk1 -> win32 (on windows) -> gtk2 -> wince (on arm-wince) -> carbon -> qt
I think this order is wrong. Qt is much more developed then Carbon.
Is there a way to verify that the LCL really got rebuild with qt?
Just go to the command line and type: ldd myexecutable
If the executable lists dependencies on Qt, it´s built for qt =)