The answer will vary depending on how you expect to use the reader, how little or how much you expect of other functions, what your patience is with not-quite-there technology, and whether you have friends with readers with whom you'd like to share books (among other things). Do read the Sept. 2011 Consumer Reports comparison of ereaders. Then update yourself on the features of the newest Kindle release (which came after the CR review). Also, see http://news.cnet.com/kindle-vs-nook-vs-ipad-which-e-book-reader-should-you-buy
You don't say why you're looking for compatibility with Digital Editions. Most ereader users don't especially care about the reader software, except insofar as it causes usability issues.
Owner of Original Nook, & Color Nook & user of Kindle for PC and frequent user of OverDrive ebooks from public libraries.