Does WPF enable me to do something that I couldn't have previously done?

Technically, the answer is "No," just like C# and the .NET Framework don't enable you to do something that you couldn't have done in assembly code. It's just a question of how much work you're willing to do to get the desired results! If you were to attempt to build a WPF-equivalent application from scratch without WPF, you'd not only have to worry about the drawing of pixels on the screen and interaction with input devices, but you'd also need to do a ton of additional work to get the accessibility and localization support that's built in to WPF, the special
handling of Remote Desktop built in to WPF so that remote applications can be rendered on the client to avoid a variety of performance issues, and so on. (Note that the optimized Remote Desktop experience only works when the server is running Windows Vista or later and the client has WPF installed.) So, I think most people would agree that the answer is "Yes" after you factor time and money into the equation!