I like this new approach even though it may require more maintenance efforts and remains difficult to debug and write during development. Why? There are certain great advantages it has:
1. It's not easy to steal your webpage's look, feel, functionality and identity (Though it is very much possible using tools like Firebug) .
2. Makes it tough to be hacked (though maybe not that much but still may be for novice it does act as a detterent)
3. A lot of Page Logic remains on the client so the responses to actions is quicker thus providing better End user experience.