One thing you should be aware of for using LiteOn DVD burners for scanning in an external enclosure:
Unlike many other scanning drives, LiteOn drives will drop samples when scanning, and the faster you scan the more samples are dropped. When the drive is in an external enclosure, even more samples are dropped.
So if you scan at 16x in an external enclosure, more than half the samples will be dropped, while a 16x scan on an internal drive might drop "only" 25% of samples.
So you might get PIE/PIF totals that are close to half that you might get on the same drive when mounted internally.
This is important to know when comparing scans.
My LiteOn drives work fine in enclosures based on Prolific PL-3507 chipset. The only problem I've had (apart from the dropped samples explained above) is that jitter scanning with earlier versions of CDSpeed didn't work. Whether this is due to the enclosure or because of the USB/FireWire connection is unclear to me.