Things were looking good for the replacement drive until this morning, when I finally got round to trying a MCC01RG20 DVD-R.
On my old drive, writing one of these at 8x led to the following Nero CD/DVD Speed graph in my Lite On LTD-163 (Dell OEM, GDHJ firmware):
Writing a disc from the same batch in the new drive gives the following result in the DVD-ROM:
Trying to read the same disc back in the ND-2500A is even worse:
Surprisingly enough, the disc failed Nero's verify as well. :Z
It all goes horribly wrong at the point where the transition was made to 6x speed - the first 800MB or so that's written at 4x is perfect. If anything, the 8x section (from about 2.2GB onwards) is better than the 6x section.
I can't see anything visibly wrong with the recorded surface of the DVD-R (no rings or similar). This is with stock early 1.06 firmware, and MCC01RG20 (Verbatim DataLife Plus 4x DVD-R, Made in India) is in the NEC media list as 8x media.
It's possible it's one bad disc. I'll try a couple more - one at 4x, and the other at 8x. If the results are as bad on the second 8x disc, are people in agreement that I should endeavour to RMA this new drive for poor DVD-R write quality?
The one thing I will do differently on the second 8x disc is print it after I've recorded it - this is inkjet printable media, and unlike the discs recorded in the old writer, I printed this one before recording it (I didn't have the printer when the old drive was still working).
I'm in the habit of inkjet printing my discs before recording - printing before recording doesn't seem to upset the Taiyo Yuden inkjet printable CD-Rs that I've been using a lot of recently (I've used about 90 in the last month). However, it might possibly be that the DVD writing process is upset by printing the disc first - though, somehow, I doubt it (particularly as the recording layer on a DVD-R is pretty much right in the middle of the disc - it's far nearer the top, printed, surface on a CD-R).
Of course, I did have to buy this drive from a vendor that's really quite slow on processing RMAs and makes you pay the return carriage (which works out at about US$10).
About the only interesting thing that this shows is that, as many people have said, the ND-2500A isn't as tenacious a reader on marginal discs as other drives.
Getting frustrated now...