With an android tablet you can download apps for all of the available ereader formats (kindle, nook, epub, etc.). Some of the ereaders limit you to their specific format although there are usually ways to get around that.
And you can download non-Amazon apps, simply by turning on the "Allow Installation of Apps" under the device options on a Kindle.
It's funny. I purchased the Kindle not for its e-reader capabilites, but to allow me to experience the tablet "experience", without the cost of an Apple tablet.
What actually happened is that it did not meet my requirements, but DW took it as "her own" to be able to play WWF, email, news, and of course to "kill those pigs".
For her, the compact design works best since we do travel quite often. While some folks don't like the idea of only wi-fi, teathering to her smart phone gives her the ability to communicate wherever in the world she currenly is traveling (BTW, we fly to Scotland next Friday).
Will we upgrade to another tablet? Only time will tell. I only know that the Kindle (or any small format device) really meets 98% of our-hers requirements for a portable "info device".
Everybody is different (as in all other areas under discussion). As for me? I still like the "base" of a desktop (with a 24" monitor) while I'm at home along with direct/cable connect rather than wi-fi when doing financial tasks, and the abilities of a netbook while traveling...