As a matter of fact, I have an outstanding bug report against the calibre package.
The Arch developers are fairly conscientious... except when they think they are right.
They haven't broken simple things like mounting devices, but they
have broken conversions and the content server (when using a password).
calibre uses internal, patched copies of cherrypy and chardet, and a forked and heavily modified copy of html5lib. System libs rule, apparently.
So for entirely different reasons, you should
still use Kovid's binaries.
This might be helpful too: Sticky:
Fully automatic calibre installer/updater for linux
(It is
on the AUR as well.)