Server streaming, though I'm not sure how representative we are. We have servers that use streaming for watching for real-time changes. Currently using BloomRPC, if that helps
Grip looks super cool - it's one of the few other clients I've seen that will render structured input fields to make it easier to construct complex messages.
If you have a more urgent need for server-side streaming support, you could also check out Protocall (https://protocall.dev - disclaimer, I'm the author) - it supports all four rpc types (Unary as well as Client/Server/Bidirectional streaming), along with the structured input field rendering and automatic import resolution (via Github repo import).
I wrote it because existing tooling like BloomRPC and gRPCurl were difficult to use for anything more complicated than "Hello, World". I was also looking for tools that would let me send protobuf-encoded requests via HTTP/1.1 rather than gRPC, which didn't seem to exist at the time.