I have not, but the table of contents sure looks interesting. Am I right that they don't do lambda lifting / closure immediately? They seem to have a lot of optimizations working on lambda expressions, and also optimizations working on records. By lambda lifting immediately I am hoping that the optimizations on records can take care of (some of) the lambda-optimizations.
The focus on lambda and record optimizations is because ML code is usually heavy with sum types (tagged unions), and it's often possible to completely unbox things at compile time.
