This looks a little like inline in F# where it allows more generic method cases than standard generics do in C#/Java. Looking at the documentation I'm wondering does it allow things like - "any input type that supports the divide operator"? It's a feature I've appreciated previously when writing high performance math code on the .NET side.
With "Expr" it should be possible to built an ORM similar to Entity Framework, it allows to write elegant queries thanks to Expression Trees in C#.