REST was good, but it is no way near to representing the native data representation. The access mechanism using xPath is also slower. I would prefer data to be JSON. After all, JSON is just a different way to write RES; different syntax, but the same semantics. I usually end up writing a JSON convector for REST data, hence would prefer the backend server to have a layer that churns out data in JSON as well.
To summarize my take on this question, I believe that XML, both SOAP and REST are a little uncomfortable due to the extra chunk of code that needs to be thrown in for rendering them. JSON is great as long as the changes that this brings about is distributed across the page. The server sending me HTML is preferable when I have to change chunks of a page, specially when they seem to be logical components of a page. Would love to hear comments on this.