See what you are doing
No need for comile, and start your application for each little change you will make.
Design your DataContext, either with our Editor and create your instances like you want, or directly call a user-defined function to create a real DataContext - it depends on you!
Perfect alignment of your layout - during design Time. You can interact with your Visual Tree and see how complex it will become with your DataContext.
Works with standard controls, third party vendors and even custom controls!
Share your Design-DataContext with your team mates. Design it once, run it on every development machine.
You get perfect support if something is not working as you would expect it.