If you look towards the bottom of this thread, you will see that these discs don't seem to work well in later ND-2500A drives. We're still trying to feel our way towards some firmer conclusions, but it seems that:
- early ND-2500A drives (including the CD Freaks review sample and my original, now failed 'Made in December 2003' drive) work well on this media and will often write it perfectly well at 8x
- more recent ND-2500A drives don't write this media well at 8x
- NEC's latest media list notes that 8x writing is possible on this media using stock firmware, but recommends 4x (unlike for all other 4x DVD-R media that's writeable at 8x, when 8x is recommended)
- the problem, if you get a bad write, comes in at around 800MB on an 8x write, when the drive switches from 4x to 6x.
In summary, though 8x is offered, I'd write this media at 4x only, especially if you have a more recent ND-2500A drive (made in February 2004 onwards at a minimum - made in January 2004 may also fall into this category). It should hopefully then produce good results. It is, after all, only 4x certified media.
It's unclear whether it's manufacture date of the drive or place of manufacture of the drive that determines the 8x write quality on this media. There's also supposedly 4 factories producing this type of media for Verbatim - the discs we're finding are troublesome in the other thread are "Made in India", apparently by the Moser Baer factory.