The keynav isn't finished, e.g. in gtk-demo the tree widget has no keynav. But it is definitely much better. Try the color selector in gtk-demo for example. App developers can set the tab order for any container.
Underline shortcuts are now easy to install and used throughout gtk-demo.
Numeric keypad support is already better in 1.3.5 and complete on my local disk. The following comments are owned by whoever posted them. Something like the edit key binding dialog in Xchat. It is something that should be in most application. If it is not put into gtklib, then everybody will start to write their own version of keybinding dialog.