Their ergonomics are (to be polite) questionable.
Tiny page turn buttons on the bottom sides?
Kindle ergonomics are barely adequate, so why are all the asian second-tier vendors rushing to copy the same flawed design?
Given how often keyboards *aren't* used, why saddle a content *consumption* device with a physical keyboard when a good onscreen keyboard (driven by a thumbstick) would serve the same function and allow for better balance and ergonomics?
