@staplebox - I've been having the same Exchange problems. I've had the problem on a Nexus S, with various ROMs, and on a Galaxy Nexus, stock. In my case, it seems to be directly related to certain emails. That is, when I receive a certain email, it will hang the connection and kill the battery. In my case it is a status email I receive from a server 7pm every day. It has some fishy header info, and Outlook reports that it may be a phishing message. I move this email into a folder that doesn't sync with my phone, and all is good.