I am disappointed with Liteon at this stage and find Optiarc 7240S a far better drive.
Last year I got 20a4p, and the firmware there is crap. It slows down even on quality SL disks cause it thinks that 12x is too fast for the media in the outer sectors. There are also bad burn spots on Verbatim DLs with PIF spikes, which never happens on Optiarc. Also, Optiarc rips DVDs about 0.5-1x faster than Liteon given the same disk.
I have 1673S and it is decent, but it does not handle DL disks well.