As pointed out, you can disable the black flash on some readers.
I tried it on my PB360 (the page did a slideshow-like fade, very quick) and found it... disconcerting. Ghosting and residual garbage wasn't the issue but rather the absence of the flash. I've gotten used to the flash and I don't notice it so I perceive the page turn as an instant page swap; the new one just pops in.
After a few minutes I went back to the standard mode.
I don't have an issue when reading on my PDA or Tablet PC or the LCD-based Jetbook Lite so obviously the effect isn't permanent.
Eventually eInk tech will get faster and the black flash will never be noticeable, even for newbies.