I preordered the DX. Larger screen and PDF support makes it a no brainer.
I strongly dislike PDF for fiction but I literally have a wall of craft books (needlearts and others) that will be great on the DX once I scan and convert them to PDF. PDF is a great document format for technical books that contain lots of tables and charts (sounds like a lot like my craft books!)
Not supporting ePub doesn't really bother me. It's one of those "It'd be nice" but it won't stop me from preordering the DX.
I'll still keep my K2 for portable reading.