Joscha (txtr staff) made a comment
on the teleread post
on the subject. I'll quote it here as it explains the dificulties for DRM protected files not purchased via the txtr Store:
As some of you know, I am working at txtr. You know what? We can not sell our books to you, no matter how much we want to. – Because books come with regional licenses, and even though they are just a bunch of bytes floating through the intarwebs, the current rights situation limits where we are allowed to let them flow to. So, no txtr Store in the US of A for now. Until we have acquired American licenses, and implemented a process to separate our platform into different regions.
On the other hand, it is technically possible to import Adobe DRM files that you have bought elsewhere into the txtr application. But at the moment that would require a working DRM pairing between your Adobe ID and txtr, which at the moment won’t work without a German authentication (usually via credit card). This is not a legal, but only a technical problem, however, and we will build a solution for it soon.
And maybe also interesting: the next comment
is from an Adobe staff member approving that this app is the first "built on the Reader Mobile 9 SDK which provides PDF and EPUB support as well as support for Adobe eBook DRM".
Well... hooray DRM