I have found fewer errors after using the FreeBSD-supplied ports of modules. I only use CPAN versions if there aren't FreeBSD versions. Not only do some installs from CPAN not work at all, they don't update the FreeBSD package database properly. 'Package blah has no recorded origin' gets old. :)

Thanks for your thoughts about non-root 'sandbox installs' for testing. I, too, have run into problems using the automated install+test system, especially modules which try to access the external world, and it's necessary to manually install such things as patches to test scripts get overwritten by the CPAN install.