REST support in WCF from .NET 3.5 is rather basic and rough when you really want to build rich and sophisticated REST-enabled apps - but it is a start.
I am sure we at thinktecture are not the only one who have build helpers and extensions to WCF's REST features in order to solve real problems for our customers, like
- Easy pipeline short-circuiting and extensibility
- Dynmaic content negotation
- More resource-friendly design
Microsoft and the CSD group in special knows about that fact and release the very first early version of the REST Starter Kit on CodePlex. Make sure to grab it and read through the docs - it tries to solve a lot of the above listed problems and even more. The features of the REST Starter Kit are meant to make it into .NET Fx 4.0, so please go ahead and give feedback on it.