It's maintained by James Newton-King, so it's in the hands of .NET royalty :)
Unlike the other gRPC implementations, it's also taken seriously by MSFT's entire developer division. MSFT contributed a bunch of performance improvements to the protobuf runtime and generated code for .NET, the Kestrel webserver team runs gRPC benchmarks, and support for gRPC-Web is baked right into the core frameworks. From a user perspective, it's clear that someone cares about how all the pieces fit together.
Even if I only briefly used it, I wish they had the same love for the COM tooling, after 30 years, Visual Studio still can't offer an IDL editing experience similar to editing proto files.
Unlike the other gRPC implementations, it's also taken seriously by MSFT's entire developer division. MSFT contributed a bunch of performance improvements to the protobuf runtime and generated code for .NET, the Kestrel webserver team runs gRPC benchmarks, and support for gRPC-Web is baked right into the core frameworks. From a user perspective, it's clear that someone cares about how all the pieces fit together.