On a side-note: I'm surprised devices like Kindle survive where superior ones like those from Sony perish simply because of the software walled garden. Not a good outlook for humanity.
Don't know about others but the first ereader i bought was a paperwhite on sale. I.e. cheap. I was used to reading on dead tree and pda/tablet and didn't see why I should get an expensive dedicated device. Only tried when it was discounted enough to be an impulse purchase. Don't think Sony ever had something in impulse purchase territory... and come to think of it, haven't seen anything about ereaders from them in the news in a long while.
As for walled garden, Calibre. Amazon can be safely ignored should you wish that.
Pick one.
When had last time Sony affordable product with good VFM not beaten by any other brand? It's same story with their smartphones and anything I can think of.