AFAIK:
The Nook hardware can read more books than any other reader, as it can read the B&N DRM and Adobe DRM.
The Sony/Kobo hardware can't read B&N DRM but that was a decision that either they or Adobe made and one that B&N
did not expect.
The B&N DRM was
intended to be less hassle than the other DRM. Unlike Adobe, the DRM doesn't have to be cleared via an internet connection -- it's a simple lock to your credit card number. It was supposed to be one step away from watermarking, and simple. And before the journeyman from space, it was the easiest DRM to automatedly strip.
Plus, yes, you can download directly from their site with
no program needed, so the books could be easily gotten no matter what OS you were running.
Now... in practice, reasonable people can disagree about how this all turned out. But I do believe that B&N was
trying to make a non-locking-you-into-a-store DRM that they honestly believed would be implemented by other eReader manufacturers. They were fairly open about the DRM and how to unlock it, and at least a few people openly speculated that B&N was being deliberately wink-wink-nudge-nudge about the unlocking tools.
And since I
do care about what's installed on my computer, I appreciate being able to download directly from the site, rather than having to go through Kindle 4 PC, Adobe Digital Editions, Sony Reader, etc.
Your Mileage May Vary.
