Memorex and I have been going back and forth about the less than stellar results I got. My theory was that it was because a) these were early samples and b) they used a TDK MID. Drives using the default TDK strategy may not give good results with this media.
Memorex came back and told me that "the Pro Gold DVDs are rated up to
8x, but that the highest quality burns are produced at the 4x speed." According to them, the final retail packaging will include this information.
Personally, I think this is pretty cheesie. If you're buying media rated at 8x, you should be able to get good results at this speed. It's not like 8x media is bleeding edge anymore.
Anyway, as soon as I can get some final, retail samples, I'll post some more tests at both 4x and 8x.