I'd buy the book in a heartbeat if it were digital.
I went paperless a few years ago, one of the biggest deciding factors was my huge collection of dead-tree books that continued to take up space even though the content was obsolete.
A $20 digital version for me would be an instant buy. A $40 dead-tree only version is a no-sale.
As someone who has moved between continents a little bit too much, a $40 digital no-DRM version would be an instant buy. A $20 dead-tree version is a no-sale.
Nope, you're wrong. I was pretty clear that those are two separate complaints. Paper is a form of DRM, and they specifically noted that as a primary reason why they were using it.
I would have (begrudgingly) paid for another electronic copy. However, had I known the first time that I'd just have to buy it again for a much-expanded 1.6 in a few months, I'd have waited and bought only the 1.6 version (assuming it wasn't paper only).
DRM is bad because it punishes your customers. I'm not giving up shelf space, ctrl-f ability, and loss of mobility because they chose this DRM.
And part of the reason that "upgrade discounts" aren't being considered is because it's impractical with a paper book. That makes sense, and is another reason not to use them exclusively. O'Reilly on the other hand, does provide upgrade discounts. This is always a better deal for both the vendor and the consumer, because the number of customers who buy every edition of a paper book they already have is incredibly small.
You have the rights to re-sell your first edition or trade it freely. You "own" the book. It's not a rental like with most digital content.