We have Software Collections for CentOS currently in our testing repo:
http://dev.centos.org/centos/6/SCL/
To date I don't think I have gotten any feedback, positive or negative, for these SCL RPMs though I know there are hundreds of people using them (or at least downloading them).
I have added the following SCL updates to the repo:
Critical: ruby193-ruby security update: http://rhn.redhat.com/errata/RHSA-2013-1763.html
Important: ruby193-rubygem-actionpack security update: http://rhn.redhat.com/errata/RHSA-2013-1794.html
Critical: php security update: http://rhn.redhat.com/errata/RHSA-2013-1815.html
If we are ever going to get these out of testing and into production, we need to get some feedback. Feedback accepted on this list, the centos-devel mailing list, or this bug:
http://bugs.centos.org/view.php?id=6719
Thanks, Johnny Hughes