Ritek ain't all that great.
I got some Ritek R01s (RiData), and their reading performance is great on my burner (851S), but is spotty on my other drives. What's interesting is the variable nature of this; one disc will work beautifully in my other drives, while the next disc (same data, same spindle, same burner, same everything, except it took place 30 minutes after the previous disc got burned) choked on my other drives.
I guess it didn't help that these were all burned at 6x...
But the point is, my experience with R01 Riteks indicate that they seem to be spotty/variable in quality.