I'll try to do some photos or some video over the weekend to compare the two devices. I just ran Geekbench 3 on the T68 plus, here is the comparison against the Lynx T68:
There is no real difference in CPU performance.
Some more comments on the two devices so far. The Lynx seems to give much better contrast, especially if you scroll a book page or web page. The T68+ doesn't seem to bring the e-ink particles back to their original darkness: when you scroll a page, it becomes lighter than before the scroll. And the time to do a full refresh (holding down the menu button) is about twice as long on the T68+ than on the Lynx. I'm guessing that this is a firmware change and not a display change.
Still, I prefer the T68+ as it is more responsive than the Lynx.
Cheers, Warren