Balsamiq

super bueno.

Daily I use this tool to validate the user interface. Whenever there is a use case which I need to resolve in our product, I directly open this tool and start scratching. Yes, I start from the scratch, by having the components separated as a collage. Then I skin the UI by placing them in the positions which looks subtle and usable. Skinning the UI with this tool is easier. Just pick and play and the simplicity of this tool is THE key thing that I like in this tool. Minimized UI is something that we can achieve by splitting the UI into different frames. We can place the components in our desired place to check if customers can feel the importance of the applied element in the page that we are building. We can easily put ourselves in the user's shoes and think from their perspective to check if we are working on a usable interface.

Moreover, the linking between the pages/tiles help us to see how the transition between each pages looks like. I usually go with RAW prototypes by scribbling in my notes. After I started using the Balsamiq tool, I go ONE STEP BEYOND scribbling. Yes, I do mocks and share with my visual designers to think through the page/feature that we want to build. This has helped our designers to a great extend. The time of making them understand the flow and designs has drastically come down. Also, the number of iterations has minimized which in turn has improved the quality of the designs that we are converging. of course, the productive has improved a lot in terms of peer-to-peer level convergence.

Overall, I love the simplicity and intuitiveness of this tool. If you are looking for a product to quickly put together a wireframe or sketch (based on rough ideas) for feedbacks or approvals, then this can be a great option for you.

I would say ease of use. It's pretty quick to pick up without much ado.