I already loved Calibre. Not just for the ebook management and sync-with-kindle stuff, but also for its ability to convert a book into other file formats. I add a .odt file to Calibre's library, and then I can turn that into a mobi or epub. Easy-peasy.
What I lacked was a decent epub reader. I'd been using a Firefox add-on to read epubs, but I wasn't really happy with it. Recently, though, I discovered that Calibre had a built-in epub reader. Not an editor, mind you, but a dedicated reader. (This is either a recent upgrade, or an old feature I simply hadn't discovered it yet. Who knows...) So I set it to be the default viewer for epub files. Now I'm happy. :) When I double-click on the Buddy epub, here's what it looks like:
So thanks again, Calibre. You guys rock. :D