XUL is the greatest thing since sliced bread, believe me.
I've seen it all. You can do it all.
Best of all, it runs in all platforms, Linux, MacOS and Windows.
Hard to beat that!
Delectate yourself with all the possibilities you can explore with XUL.
Check out the Desktop of the future.
* Note:
It only runs in gecko browsers like Firefox.
But don't despair, XULRunner is on the way ;-)