We are using two current Decklink studio cards in a Mac Pro in our OB truck. The system is used as a master recorder and so far have been working well.
One issue I have though is that the Blackmagic system preference panel reports for both cards "no reference input detected" even though we are feeding sync to the reference input. We have tried tri-level sync and regular black/burst but no luck. I have checked with a CRO that the sync is actually there at the input to the recorder. We are running the latest version of the software / firmware on OSX 10.6.
I also have the same issue in our studio on an older decklink card installed in an XP SP3 PC.