Lag
The Kindle has a physical keyboard for entering URLs. While the Orizon's virtual equivalent isn't hindered by the Kindle's clumsy system for entering symbols and its keys are sufficiently spaced to minimise mis-hits, you'll invariably find the screen struggling to keep up with your taps.
And with no cursor, even one that doesn't flash, it's hard to know whether the field you want to type into - the space for a web address or Google's search field, for instance - is the one that's going to receive your input.
The Orizon's e-paper screen comes from SiPix rather than E Ink
The lack of feedback is incredibly frustrating at times, as is the general speed of the device. There's always a brief but very noticeable lag between tap and effect.
This is true of all e-book readers I've looked at, including the Kindle, but here it seems somehow exaggerated because you're steered to do everything by touch. Yes, swiping to turn a page does seem more natural than pressing a button, but if you're flicking through pages, it's pain in the proverbial. Thank goodness Bookeen has included its customary five-way navpad for quicker page-to-page movement.