It's niche, but I wasn't really able to find anything else like it. I wanted to project our some retirement scenarios and my options seemed to be:

- Any of a few dozen "retirement calculators," each consisting of 6 fields and very simple outputs

- Building out a series of buggy spreadsheets

- Projection Lab

After messing around for it a bit, it was a "shut up and take my money" situation. It was cheap, it was powerful, it was nice to use, and it has been the foundation for my personal financial strategy for the last few years!