This project is now [unmaintained].
Pacaur is an AUR helper aiming at speed and simplicity, designed to minimize user prompt interaction and to use an uncluttered interface. It is built upon the well designed cower and expac C backends.
Pacaur is targeted at advanced users who want some degree of automation for repetitive tasks. It is designed upon your assumed knowledge of the manual build process with makepkg and its configuration options, the AUR as well as pacman, cower, sudo, and gpg configuration options. If you want to make full use of pacaur, you have to master these tools first and be ready to deal with the expected unexpected breakage.
See also Why pacaur sucks less in the official forum thread.