Every few months or so I run out of patience with C++ and wonder about the alternatives, of which there seem to be very few in HFT. Jane Street stands out for that reason. It's a smaller talent pool but I don't think it's a subset of those that the C++ shops can attract.
Rust is getting pretty popular among low latency firms. Many of my peers (myself included) would definitely show interest in a rust shop. OCaml - not so much.
