As an aside, JS does definitely make things feel slower than native in some instances. Regardless, how does generating JS from OCaml make things faster, I wonder?
I think our app is as reactive as a native app despite javascript; if you see any lack of responsiveness I'd be interested in knowing where so I can improve it. I do however agree that it "feels" different on OSX, since you don't have the native animations and look & feel, but I don't think it's related to speed.
Regarding OCaml, using such a strongly typed language enables heavy abstractions without a runtime performance tradeoff, leverages the static optimizer of the OCaml toolchain and outputs optimized javascript (asm like). This is, I would argue, hardly achievable by writing directly plain javascript. Note however that there are other tools that target javascript with similar benefits.
Regarding OCaml, using such a strongly typed language enables heavy abstractions without a runtime performance tradeoff, leverages the static optimizer of the OCaml toolchain and outputs optimized javascript (asm like). This is, I would argue, hardly achievable by writing directly plain javascript. Note however that there are other tools that target javascript with similar benefits.