I use Tk (but not perl/Tk, rather Tcl::Tk module), and I have little need to search something different.
I tried some native-Win32 programming via perl also, but got rid of this way in 199x
Here are my experiences for your list:

• Gtk+ is advanced but complicated to use. It could be more advanced compared to Tk in some aspects, but due to its size there are many drawbacks
  Its like programming C these days. You really must use C for some kind of projects, but I prefer Perl for 99% of tasks.
  Its size makes it difficult to move, also I am sure it ill never be in PocketPC.
• QT - nice look, but cost too high. When I hear voices around QT "if you're good programmer you'll cover this cost quickly within your brilliant programs, otherwise QT not for you" - stupid bull*hit; if I have extra $3000 I'll buy notebook PC for my toliet room.
• WxWidgets - I did very small research on this (hardly going further running few demos and looking through examples)
  Very impressive, high potential, but not enough for me to move from Tcl/Tk

BR,
Vadim