We directly stream arrow across devices, skipping grpc indirection / confusion, and have done that since near the beginning of arrow. Others do too, works great :)

Flight is interesting to us bc they're thinking through parallel i/o. I'm guessing grpc overhead there is more tolerable, though yeah, I'd be curious. I had similar initial reservations, esp as we were happy to remove slow google protobuf stack stuff as part of our switch to arrow :)