I can empathize with anyone who has had problems and spent time troubleshooting. I have too. But some people change drives more often than they change underwear, when usually a less drastic change -- to a different hardware config, different firmware or different media -- will solve the problem.
I'm not picking on anybody in this thread, but I've seen lots of "brand x burners suck" posts here and in other forums from people who have not followed the installation instructions and have the jumpers set wrong, are using a bad cable, are having problems with non-MS IDE drivers, don't have DMA enabled, don't know how to run their burning apps, are trying to copy on the fly from scratched rental discs to the cheapest no-name media they can find using outdated software, etc., etc.
Back to the car anology, if you put a Porsche engine in a rusty Pinto, fill the tank with kerosene, throw on some recap tires and take it to Watkins Glen, you're going to be upside down in the weeds before the first lap.
All I can say is that when I bought a 401S, it worked out of the box with good 4X DVD+R. I converted it to a 411S and it worked perfectly with good 4X DVD-R. I modded it to 811S and am getting eight-minute burns with excellent Kprobe scans and near-universal compatibility with bitsetting.
I just finished three straight on-the-fly copies from DVD-R to DVD-R using my LTD-163 and LDW-811S, and got three perfect dupes with the highest max PI being 31 and the highest max PO being 6.
I liked my burner so much I bought one for my son, and he's getting the same high-quality burns on his 401S@811S. Could be just good karma, or we got the only two good ones LiteOn ever made, or it just could be that if you set them up right and feed them good media you get good results.
People who expect something as complex as a DVD burner to work right out of the box on any hardware using any software and write to any old wet beer coaster are deluded, IMHO. LiteOn can't do that, but neither can NEC or Pioneer or Plextor.