In a post to the Exchange Dev blog, Michael Mainer announced an update to the EWS Managed API today...

"The latest release of the EWS Managed API, version 1.2.1, is now available. The EWS Managed API 1.2.1 includes new Exchange Web Services (EWS) client logging features for Exchange Online as part of Office 365, as well as some minor bug fixes."

The Exchange Online client logging features are very useful.  Even if you don't use the EWS Managed API you should understand what the RequestId and X-ClientStatistics headers are and how to use them.  Here is a snippet...

"The RequestId header contains a GUID value that uniquely identifies your request in the Office 365 server-side logs across all the Office 365 data centers...

You can use the new X-ClientStatistics header to provide additional logging information for Exchange Online. You can enable additional performance logging for Exchange Online by providing the following information in your requests:

    • The RequestId received from a previous request
    • The client-logged roundtrip time between the request and response
    • The SOAP action..."

You can download the EWS Manged API version 1.2.1 here:

http://www.microsoft.com/en-us/download/details.aspx?id=30141

**Note these updates have not been applied to the EWS Java API.