On the one hand, this trait made me fairly pleased with Sony's Reader Library when I first started using it. Moving files to my PRS-600 was so simple, downloading and viewing files even more so, and arranging them in bookshelves proved to be surprisingly convenient once I started amassing books. And taking notes on my computer? A cinch. But it's an annoying, frustrating program too. The inability to adjust metadata means that many of the files I've acquired have bizarre/inaccurate titles and authors, making it incredibly difficult to keep track of where my books are at, once on the Reader. I started searching for ways to change the settings, certain there must be some simple solution. Instead, I kept coming across the name Calibre again and again. I finally downloaded it, after using a computer for a couple of weeks that seemed unable to use Sony's program (it turned out the problem was that the Reader Library had been installed on an external drive to the computer that was no longer there...). The results? Calm, blissful, and altogether impressive. I am now a Calibre convert. Sort of.
Calibre doesn't resemble Sony's iTunes-esque library at all. On the one hand, it's simpler, with large, easily recognizable buttons along the top displaying the many available options. On the other hand, it's more complex, because -- it has buttons along the top displaying the many available options. I don't mean the option of "change author", "change title", etc. No, it's "edit metadata" and "convert format", both of which lead to new and seemingly complicated screens. Except there's really nothing to it. Within seconds, I'd managed to figure out how to maneuver Calibre's basic options, even picking up the quick keyboard commands (they're entirely intuitive - v for view, e for edit, c for convert, etc.).
There are two main features that make Calibre worth your while, no matter what eReader program you use otherwise. The first is the ability to convert files. Almost every format can be converted to something else (I think .doc is the exception), so if you've found a great book in PDF but don't like how it looks, hit a couple of keys and bam--ePub it is. I'm not sure if it works for .azw (Kindle) files, but the open screen indicates that it's a Kindle compatible program too (through .mobi, I think). For the rest of us, though, it works like a charm, even if converting PDFs reveals funny glitches like page numbers in the middle of the screen.
The second interesting feature is "Fetch news". Upon command, Calibre connects to the internet and downloads the most recent newspaper or magazine from a multitude of sources (in a multitude of languages), making it possible to read The New England Journal of Medicine and then getting updated with The Chicago Tribune. For those with Kindles who pay for some papers, this feature may seem silly (particularly since one needs to connect the machine and the fact that often the papers are incomplete without a subscription...) but in all honesty it's great for me. I recently took a flight across the Atlantic and instead of buying my typical Economist magazine, I downloaded the free (and mostly complete) version to my Sony and enjoyed it on the flight for no extra charge. Calibre automatically downloads the papers into the suitable format for your device (specified upon installation), complete with internal links to specific articles, to menus and the black-and-white pictures.
It's not a perfect program. Far from it. It's slow, somewhat unorganized at times, and cannot actually be used alongside Sony's Reader Library. Technically. In reality, it's possible to use both by taking advantage of Calibre's useful features and avoiding letting it come into contact with the actual eReader. Still, it's an added step and an added hassle. But for the ability to fix those pesky PDF files that come with crazy metadata (by converting them to ePub with the proper info, or self converting to PDF, as strange as it sounds), for the newspaper feature, and for the ease with which I figured out theoretically complex stuff, I give Calibre my stamp of approval.