What-you-see-is-what-you-get editing makes Slingshot a user-friendly application that allows you to know exactly how a page will look in the live environment, even as you're creating it! You can even take a page out of the context of the adminstrative site by using the Preview function. Being able to see your site from the end user's point of view allows you to determine what works and what does not, and fix it as you go - there's no switching back and forth between screens.

But don't think that you can only view individual pages - because you work on a staging environment that updates as you save, you can also view your whole website at once, without worrying about it being viewable in the real world.