Support for printing will in fact be coming in version 0.5. I’ve committed (to my branch) a new printing framework that fixes the bugs in the old one. Also, I’ve committed some PDF changes. There is now an any2pdf app which will allow for conversion of any supported ebook format into the PDF format. PDF files will also have the first page used as the cover image within Calibre’s library.
There are a few things to know about the printing support. It’s only in the ebook-viewer application. It uses a print style so what is printing may not look exactly the same as it does in the viewer. Page breaks are not honoured, this is to save paper. Javascript is currently being stripped from the book. This should only have an impact on ePub books that utilize Javascript (I don’t know of any that this will be an issue).
If you want a perfect printed representation of an ebook as it is viewed in the ebook-viewer application use any2pdf to convert the ebook into a PDF file.
Just like with the last implementation for printing this could change at some point. However, this version has been deemed good enough for inclusion.