I have a Plextor Premium and 716A with the latest firmwares. In Plextools when I try to read a heavily scratched CD it would hang. I didn't think much of this, but when I try to back up a heavily scrached DVD using DVD Decrypter, I get seek errors after the first error and it's unable to read much of the DVD afterwards. However, with my Liteon SOHW-1673s JS05 using DVDDecrypter, I get L-EC (?) errors, and after a while it will start to read the disc again. I get the same results with my LTD-166s, though with slightly more errors.
I thought Plextors were good readers, I didn't expect a 2 year old liteon DVD-ROM to be better than the newly released plextor DVDRW at reading dvd media.