If you install current ADE3, some books you download to it may not be able to be transferred or downloaded to mobile devices.
— Micah (@micahsb) January 25, 2014
This has also been confirmed by a couple other users (one, two). According to Micah Bowers, CEO of Bluefire Reader, the bug is only affecting a small fraction of newly downloaded ebooks and it is blocking users from transferring their purchased ebooks to their ebook readers. That's not what one user reported on Twitter:
I had a bunch of books on my laptop & yesterday ADE wouldn't let me access them. I purchased them 7 years ago. So NOT happy.
— Rebecca (@RebeLovesBooks) January 27, 2014
It's not completely clear whether the new DRM is specifically to blame and not simply the fact that major new app releases are sometimes buggier than one would like, but Adobe has been apprised of the issue and I am sure they are working on a fix. But until they release an update you probably should not install Adobe DE 3.0.
What we have here is an example of why you should never install new apps until after someone else has had a chance to be a guinea pig. Adobe DE 3.0 included a few minor improvements, but its chief noteworthy feature was the new and supposedly uncrackable DRM, and until I knew for sure that it wasn't going to bite me in the ass I wasn't going to install the update.
TBH, I wasn't going to install the update until I knew for sure that the DRM had been cracked, thus enabling me to protect my purchases. I'm told that has not yet been accomplished, but I would bet that someone is working on it.