Just another anecdotal account: I didn't buy much from Amazon back in the day when I was all epub, but once I came around to Alf because it was too inconvenient not to have all mycurrrent books on all my devices I bought quite a bit. If future purchases can't be put on my Kobos, that's the end of that, though; I've not yet transitioned to Kindle (although I have no doubt I'll be there eventually, as Kindle will be the last man standing IRT e-ink devices).
I'm also on the verge of a new computer. For various reasons including this, I should keep Old Bessie running, but still, quelle inconvenience.
Funny. What with Kobo's going over to VIP-only discounts and Amazon's cracking down on de-DRMing, I may not need
this thread any longer. Oh, the irony! My overbuying in recent years is looking like a better and better investment.