Anything running on eInk will have a slower refresh compared to an LCD--it's not a fair apples-to-apples (no pun intended) comparison. My experience on the Edge is that it does take a half second for what you write/draw on the Journal or Reader annotation to appear. But for me, the advantages of eInk over LCD for heavy reading outweigh the slightly faster refresh.

If eInk survives the iPad, then future generations will likely have faster refresh (and color). But given the physics behind the technology, it will probably always be slower than an LCD.