The explicit behavior customers are reporting have now been confirmed. As folks have reported in the comments here the following scenario is the only impact we are aware of
Products:
Exchange 2010 SP1 RU3
Blackberry Enterprise Server (all versions)
Issue Description:
Users are seeing a duplicate message in their sent items on the device when a message is sent from the blackberry device. The duplicate appears only on the Blackberry device, not in Outlook or OWA. No duplicate message is transported through Exchange.
Current Status (3/15 12:30pm):
The Exchange Customer Experience team is actively working with the RIM Engineering team to identify a resolution to this issue. Once we have a candidate fix we will post further here on the EHLO Blog.