As for GUI, depends on how complex it is, Tk has no problem to deliver, but be careful, Tk code is extreamly difficult to layout and maintain, I tried Tk in one of my project, and to be frank not very impressed. Java is one of the good choices for GUI.

How do you figure? Swing and AWT are a mess. You need lines and lines of code to do what you can do in just a few lines in Tk. I'd much rather work with Tk's geometry managers than write all sorts of code to layout a Swing form. Maintenance of Tk isn't "extremely difficult." If you break down your windows into classes, maintenance becomes very simple.