i think you'd better - search or wait for new devices with http://www.pixelqi.com/ displays, by that you could receive the inky e-reader and functional tablet - all in one.
Android devices being or not - open sourced -- doesn't give any advantages over other 'mainstream', as for me. Particular advantages could provide the devices - with ability to easily run Maemo/MeeGo or other normal GNU/Linux distributive. -- these, which you could operate fully rooted easily and without loosing the warranty - just like you may do with your PC's, currently. These devices are pretty rare and often come with outdated hardware -- that are the problems of 'industry' 'preferences'. There are people - trying to solve these problems - manufacturing their own "Open" devices on which you could easily install one of the fully-operational GNU/Linux distributives. But, given that on this list - you don't see many.. if you want all the best affords you might want to be combined in awesome product.. you'll see that it is pretty challenging to find and receive :) You could wait or try to help some initiatives like - http://lkcl.net/linux/modular.computing.architecture.html by your donations or etc. And finally, after some year(s) - receive the product of your dream.. As you see - people often buy what the near market proposes and doesn't bother about http://www.defectivebydesign.org/ or other FLOSS community Notices, by that - throwing the money into closed/defective systems. For example, as a 'practical solution' - you could buy some of these inks of these you'v mentioned, root it, install - http://meeto.us/ and live happily with some cloud reader, proprietary or not. But - doing like this you wouldn't change the market behavior and by this - would increasingly **** with your own hardware to make it work for you, when you'll come to some 'advanced' use-case. In some cases - making it work for you would became nearly impossible, even if you'd beg the company to make what you dream of - in some new firmware.
