We are currently starting developments in two sublimely disparate systems, Eiffel and ABAP/4. I have built a noweb template for Eiffel and will be starting one for ABAP in the next couple of weeks.
noweb is both a common editing environment for all these various languages, and a fundamental design tool. I rely quite heavily on conditional tangling (with nocond) to produce testing and production versions of the same code; it has effectively eliminated earlier problems where subtle alterations could occur after testing and the production code wasn't actually the same as what had cleared the tests.
I also rely on the ability to implant stream-of-consciousness descriptions into the code. Far better than in-line comments, these off-the-cuff chats I have with the page about what I'm thinking turn out to be a major factor in getting up to speed when returning to code after an absence.
While I often use some portion, or all, of the weaves for communication with clients and colleagues, I continue to remind other programmers that the major benefit I derive from noweb is in design, not as some "extra" layer of documentation.