Here are a couple of Exchange backup tips.
Doing a backup of Exchange and the Mailbox level can take a long time. Rather than just backing up all of them, pick those users who will have ciritical data (such as developers). A quick rule of thumb: back up the mailboxes of all those who are higher in the food chain than you are!
If there is not time to do a compare on the whole backup, select the volume with the most critical data, and do the compare just on that.