I bought the external I/O Magic. I burned a disc with the G7C9 firmware that came with the drive. The quality scan of that burn looked terrible. I switched to retail firmware and the burns now have great quality scans.
I do have 20 'Teon' CMC MAG E01 discs that I bought from Staples for $5. The firmware 47L9 used with external burners had trouble with these discs. But, they burn GREAT with the B7P9 firmware. (Both on my external I/O Magic/BenQ and my internal BenQ unit.
I have a hand full of different media. The ones that burn the ABSOLUTE best are Taiyo Yuden +R, 8X (YUDEN000T02) burned at 12X, although Verbatim 16x burn really well at 12x too.