One of the things that was announced at MEC recently was Microsoft's Cloud first strategy with Exchange, which basically means that new feature will appear in Exchange Online first and then at some later date make their way into the OnPremise version of Exchange. One of these new cloud first features is the OData API for Mailbox data which is a REST based API for accessing mailbox data (as apposed to EWS which is a SOAP based API for accessing mailbox data). JSON and REST have become the standard for building WebAPI's over the past few years and every man and his dog (Google, Facebook,Twitter,Apple etc) are now using this so its exciting to see Exchange make this move. If you want to find out more about it and you have a couple of hours to watch some good video's I would check the following two presentations from MEC http://channel9.msdn.com/Events/MEC/2014/EXT301 and http://channel9.msdn.com/Events/MEC/2014/EXT304 which will give you a good grounding in both oD...
Pushing the Envelope in Messaging and Office 365 Development