Using Mockups feels like drawing, but because it's digital, you can tweak and rearrange easily. Teams can come up with a design and iterate over it in real-time in the course of a meeting. Product managers, designers, developers, and even clients can now work together in the same tool to quickly iterate over wireframes, before writing code.
The first impression might be disorienting. There are very few interface elements on the screen. Start exploring however, and you'll find out that Mockups is filled with powerful yet only-visible-when-you-need-them features.
Getting your ideas out should be effortless. We sweat the details so the app gets out of your way, instead of forcing you to learn it. You won't see many dialog windows interrupting your flow, and you won't have to twiddle with options all the time.