Don Box has come out in defense of Microsoft's support of REST technologies a number of times. And this year we've started to see what else is behind the curtain, with project Astoria. Still being designed and built, but with bits available and integrated into VS2008 today, Astoria includes both local (your own machine/datacenter) and cloud services for data storage that support HiREST, relational modeling, and support for various data formats (JSON, POX, Web3S [the last a play on, and jab at, S3?], ATOM).
If you haven't seen these services, you need to check them out. In addition to being technically interesting (e.g., since queries can be expressed via REST-style URLs, your network appliances and front-end web servers can actually participate in execution or caching strategies!), these services are likely to be a big part of the web service landscape.
Whether you love Microsoft or not, it is fairly clear that the original ASP.NET SOAP implementation (and client generation) were years ahead of anyone else in terms of no-nonsense ease of use, compatibility, and extensibility.
These SOAP components were made available to developers in 2000 or earlier. They brought things like "Type [WebMethod], ok now you have an XML-RPC SOAP service. You're done, go home, have a beer," while Java was still trying to figure out how which alphabet to jam into the end of their JAX* wildcards, and inventing APIs where you just start off with a nice ServiceFactoryBuilderConfiguratorFinderInstantiatorFactory and go from there.
Why rehash this history? Because in its final form, the Microsoft solution is going to be influential. They may be late to the party here, but don't discount them.
Enterprises need service description layers for REST. Someone is going to give it to them in a way that they can use it. And an Amazon-S3-scale relational data service in the cloud (no, Freebase and the like don't count) could be really interesting to everyone who doesn't have enterprise, need-my-data-physically-in-house requirements. With ActiveResource a core part of Rails 2.0, I could see building read-heavy apps using caching and Astoria, and no local database at all! My clustering problems (and expense) have all just become someone else's problem!
There's something else to see here too: read the Astoria dev team blog and the comments. You're watching Microsoft designing and implementing a big API in real time with interaction from the community. Don't look for an open-source experience -- you can't check out the code and send patches. But there is a lively discussion going on between the development team and outsiders to try and come up with the best solution that fits the constraints.