So the point of view on SC matters.
If you live the EL/EPEL world and have some Fedora, SC make a lot of sense.
If you only use Fedora, Fedora moves fast enough to likely not have a ton
of use for them. I think that's been hit.
As for Puppet, I've proposed several ideas on how to improve Puppet on
Fedora/EPEL and basically it turned into a bitch-fest. I'm still working a
plan on it. When a distro chooses "First" as one of their foundations,
that comes with problems. Fedora is the first (and only of the 8 major
Linux distros we support) to only have Ruby 1.9 support. We have a puppet
that fully supports Ruby 1.9. It didn't make it into Fedora 17. I've been
working hard to see if it's possible for F18.
I could get into more discussion on Puppet with EPEL/Fedora, but that's
been covered.
Back to software collections: I'm in favor for EL. On Fedora, meh. In fact
some of CentOS people have already spoken with Puppet Labs about maybe
doing something with SCs for EL if needed.
(Obvious disclaimer, I work at Puppet Labs)