I generally make my desktop interfaces with Qt, but some recent TK screenshots convince me Tk isn't just ugly motif any more. Additionally Tkinter comes bundled with Python, which makes distribution easier.
So is it worth learning or should I stick with Qt?
The answer to your question is a resounding yes.
Qt is good, I have nothing against it. But Tk is better and far easier to use and quite well documented - not just on the Python webspace, but there are also many third-party tutorials out there. This particular one is where I learned it from and it has been quite infallible in serving me.