Ok, a few years ago, there was a more detailed discussion here, but things have settled meanwhile!
Many arguments against tcl/tk don't exist anymore: Tcl/Tk is precompiling, resources (CPU, RAM) are available and structured programming in tcltk is possible!
Esp. itcl is awesome! One gets the whole might of OO programming! And the easyness of a shell! It is just great. I want to thank the programmers and contributers of itcl, tcl/tk again here!
A few more pros:
Any search machine will find you tcl, tk and/or itcl websites! But you could try these: