Chimayo SSIS was conceived as a way to reduce the complexity of a hundred SSIS packages operating and being maintained for a single product.
I had looked at the market and didn't find anything that really met the goals I had in mind:
BIML, BIMLScript and the BIML API are robust offerings for SSIS development, but they weren't a good fit for my needs. I was looking for a much richer development experience than working with XML and ASP/PHP-style scripting. I wanted a functional-first experience with immutable data types, pattern matching and compile-time syntax checking.
The BIML API gives a bit more in this direction, but without immutable data structures and with an object-oriented approach, it wasn't what I was after.
If BIML, BIMLScript or the BIML API work for you, then don't change to Chimayo. They are mature, well-supported and cover far more features than this project is likely to ever support.
Functional programming languages excel at data transformation, and F# is a great functional programming language. Code in F# is generally much more readable than in other .NET languages, supports higher level constructs much more simply and has direct support for higher-order processing with pattern matching, discriminated unions, type inference and function composition.
Chimayo links two of my likes: spices and a local Belgian beer. What better reason could there be?