The fact is, most people who buy a particular brand of ereader tend to stick with that brand. Besides, if you've bought a Kobo Aura HD, you are as locked in to having to stick with epub stores and therefore locking yourself out of what is one of the best bookstores available - if that's not an issue for you, why would you think it's an issue for me on the other side of that? (Which I'm not since I own a Sony and buy my books from whichever store I feel like regardless of that).
As for there being no guarantee the Kindle will still be top quality in future, I'd think buying a device from Amazon over just about any other gives you more guarantee of that.
And regards DRM. See how you feel about your ebooks still with their DRM when you find yourself in the position of having a hard drive failure on your computer, or buying a new PC, and because you already have Adobe registered on a few other devices you hit some hassles because you've ran out of Adobe registrations and can't read your ebooks.
If you are happy to think Amazon goes around closing accounts for no reason, removing books from your ereader, etc, that's up to you.....
I prefer to choose my ereader for its merits, immaterial of who sells it. And the best user experience (which includes a high level of customer support) is one of those merits that led me towards picking the Kindle PW over the Kobo Aura.
I am sure if I had opted for the Aura I'd have been pretty happy with it, although if Sony had give the T3 a built-in light, I'd probably have went for it over both the PW and the Aura..... poor me, I went for the PW and now I'm locked in and limited.
