Firstly, he works at Microsoft Research in Cambridge. Secondly, he's using MSR's Z3 SMT solver which maybe has really nice F# bindings. Thirdly, he suggests som

Firstly, he works at Microsoft Research in Cambridge. Secondly, he's using MSR's Z3 SMT solver which maybe has really nice F# bindings. Thirdly, he suggests somewhere toward the end that he finds Visual Studio + F# nicer than Emacs + OCaml for doing exploratory programming, though he doesn't exactly explain it at all.