I thought I had posted about this before! But I guess not...
I had the idea for versionpkg while creating the Arch CVS/SVN PKGBUILD guidelines on the wiki.
versionpkg is a very simple script that allows you to easily update your CVS and SVN packages without having to edit the PKGBUILDS manually to enter the date or revision number.
Simply run this script rather than makepkg in the build dir. This script completely removes the need for backtick execution in PKGBUILDS.
You do need some special variables in your PKGBUILD but if everyone follows the guidelines when submitting to the AUR everyone can use versionpkg to stay up to date.
You can get versionpkg from [community] simply by running pacman -S versionpkg