The sketch had six panels. The first release had one. We wanted to help people find a document they had just uploaded, and most of the interface had very little to do with that job.
So we kept the upload button, showed a clear receipt, and gave the document a permanent link. That left us enough time to make the error messages useful and the keyboard path predictable.
The smaller version taught us more because people actually used it. The next feature came from watching where they hesitated, rather than adding another panel from the sketch.