After a few weeks designing prototypes of user interfaces and forms for some applications of a project, I must say I'm surprised of how complete and easy it is the design of GUIs with Visio 2003.
I've designed forms that anybody could think are actual screenshots of a working prototype, very detailed, from the minimize or close buttons, to icons, toolbars, statusbars, controls...
The docking system of elements is perfect (building a toolbar is even easier than in Visual Studio .NET), and if we have to admit something about Microsoft, is the easy of use. Even not having read a single manual or tutorial I haven't had any problems finding options or parameters with ease.
After having tried another applications like SmartDraw (versions 6 and 7), I prefer Visio 2003.
The only complaint we can find (well, not really a problem for me, but my project manager pointed it out) is that the GUI is 100% "XP style", everything with the rounded Windows XP controls look.
I haven't searched on internet for a "classic" GUI pack (Windows 2000 and previous).
As usual, it is only my personal point of view, but I really liked it!