For me, it's isn't the eInk screen that makes me hate my PRS-T1 sometimes. Yeah, it flashes. Big deal -- so does a page that I turn manually. But the screen is too small, smaller than a normal book. But even that isn't the problem.
The problem is truly awful quality of the software. It turns two pages, often, when I press the next page button. The library software crashes after pressing next page ten times. It only shows 9 books per page. The stupid thing thinks I've "read" a book as soon as I've opened it. It doesn't handle tags. It crashes when trying to create collections. You cannot cycle through the books; the start of the list is the start, no jumping to the end or the other way around. Search is often broken. The dictionaries are crap. There is no cross-reference between books. If a chapter has a hundred pages, after page 20 it gets really slow, I guess because it layouts every page up to the page it wants to show, for every page. It sometimes start to auto-turn pages. And so on. And yes, this is fully updated firmware.
I think it's the software rather than not wanting to carry two devices that is going to kill ereaders.