Mock-ups are very powerful tools to communicate requirements with clients, however it could be very time consuming and costing to create a good looking mock-up. Also, we don't want to "create and throw" our mock-ups, they should be picked up by developers and add features on top of them once the client approves the work.
Using Expression + SketchFlow, you can:
✅ Figure: Good example - Expression + SketchFlow
Read Do you conduct specification analysis by creating mock-ups? to learn more about other mock-up types.