I agree - JSON-RPC is simple to use, parse and understand. Plus I feel it makes more sense when you are triggering computations remotely rather than querying.

At StackHut (http://www.stackhut.com) we're hacking on a platform that takes code you've written and hosts the API in the cloud over JSON-RPC. We think it's pretty cool and would love to hear from others doing interesting stuff with JSON-RPC.