While I'll agree using Gtk is *harder* than using Tk, the result is a much better user interface. No offense to Tk, but when I see an app written in it I immediately think "ah how cute, a GUI app written 10 years ago" even if it wasn't.
I guess it really depends on your target audience, but I don't even use Tk for personal GUI apps any longer.
One way to get around some of Gtk's code complexity is to use the Glade IDE to build your interface and then simply "load" it with Gtk2::GladeXML. This limits your code to only writing the callbacks, which is the interesting part anyway.