Unfortunately, browsers don't give very much (if any) control over the networking components -- so you lose out on possibilities for much observability, you can't do things like implement HTTP/2 if your browser doesn't already give it to you, you can't tune DNS stuff at all, etc. Especially as, right now, it only supports gRPC, which requires a proxy on the server side if you want to use gRPC from the browser.

What benefits would you like to see for a browser-based app?