Wyatt Software had one successful product, a portfolio optimizer based on efficient frontier calculation, when it followed its customer's advice and set out to build an integrated trading and accounting application for bonds.
I worked on this for three and a half years. I had strong opinions on strengths of objects in general and Smalltalk in particular. Over the years I found ways to deliver value regularly while preserving those strengths.
Many billions have been managed with the product which has lived well past typical PC software from the '80s.
I told my research colleagues that I was doing field research in object methodology. This was not far from the truth. I often give the example of abstractions discovered late in development. Following an agile method of my design, we found that we could substitute these late discoveries and benefit accordingly.
I discovered Advancers when hunting bugs in our tax reports. Traders don't care how they make their capital gains, but the tax man does. Only satisfying the latter did the abstraction surface. I described it to our domain experts and asked what it was properly called. They had no such abstraction in their vocabulary. Hence only agile debugging could surface it.
See more of my product work at Wyatt Software.