I do GUI Perl programming for Windows, using Win32::GUI. It's not exactly easy, but it's not too bad either; most problems can be solved given sufficient STFW time. I do sometimes feel that the time spent solving GUI problems is chewing up the time saved by going to CPAN for the core logic, though, which would be my number one complaint about Perl.

Number two complaint -- threading. I have to write sequentially, because forking uses so much memory and threading just doesn't.