Like a few have pointed out, it depends, but even then not the whole beast. Certain few diagrams are useful in the early stage, where having diagrams is fastter to communicate ideas and concepts across. Other than that UML is a wastage of time as the software base evolves - it cannot pace itself well to that dyanamism and agility; it has no inbuilt dialectical characteristics. However, document core stable parts could be done. I personally do not know any body who does though.
Thank you for sharing. This has given me good ideas to follow through as I try to build up my product. How much resources (capital wise + hours) did you expend? You say in earlier post, 250K bootstrap fund. What percentage on this particular effort?