There's no need to wonder. Get the Serial # and manufacture date off the back of the unit. Get the several firmware numbers by following the procedure described in this thread which will cause them to be displayed on the front panel. Send an email to the tech support/service email address at Denon (not the customer service address) including all this info, and ask them if there are any upgrades not yet applied for your unit and what they do.
Typically you'll get a response back in just a few days.
I believe the IEEE1394 fix was the only one that required sending the unit in. Denon will mail you a disc with any firmware upgrade you need, and it can be installed easily at home. I don't believe there have been any new firmware upgrades since last July, but again, it's easiest to just ask them.