well, I own a duo and a duo RX.
I havent tested the rx yet, but my duo is mint! it plays CD-Rs the only issue i had with it was that the psu I was using wasnt up to scratch so the drive didnt spin, ive got a ninja PSU now and it works like a dream.
The R just has lost the CD tray lock and is restyled as far as I know. The RX is the same machine as the R but just with a six button pad. My duo is up for grabs if you know anyone £150 and I will throw in some cdrs of spriggan, drac-x,hellfire,r-type complete and gates of thunder.