As cool as this feature is, I think I'll stick with my current method.
I prefer to download the ebooks and add them to my calibre library. This lets me control the metadata, available formats, and generally manage my ebook library in a single location. But that doesn't give me an online backup, which is what O'Reilly offers above. But that's okay because I also have the Dropbox app installed on my laptop. It's set to sync my calibre library folder with my Dropbox account.
It takes a little more work but that's a better option, don't you think?