I've just bought myself a E10N, and I generally like it, but I am unable to burn faster than 12-13x (I mean actual speeds). It goes normally upto 11.5x or 12x, and then it starts loosing it's buffer, first 80-90%, then 50%, then 30-40%, and slows down to 12-13x speeds. ImgBurn graphs starts to go dizzy that time.
I can actually read files from the harddrive at 38 MB/s, I write from a VIDEO_TS folder, I've flashed J07 fw, and I don't use any other USB devices. Nero reports burst rate of 26 MB/s, and I use ImgBurn via STPI.