Been working on this with Microsoft last night and we found that in OWA & mobile email and calendar functionality is perfect.
This main issue is strictly with Outlook (x 1300 mailboxes) it seems to be ok as far as receiving and sending. Most of the time. When I click on calendar and add an event it says event could not be created but I also had my OWA open and it did create the event. At that point I went back into Outlook mail and it wouldn't show me any emails and basically hosed Outlook and throws the error. "Operation failed" and no emails show up al all until you close it and reopen it.
Even the Techs with Microsoft said they've never seen this before. The last thing we tried was create a test account and added it to my outlook and it worked perfectly. Been waiting for them to call back since 1:30am they are supposed to call me in 50 minutes.