You have obviously never tried FF in enterprise environments. The original poster is correct, it can't be configured via GPO, only config files which the users can modify. I know there are work arounds for that but its a lot of messing around especially since you can configure and lock down both Chrome and IE via GPO.
Releases are still too rapid on the enterprise release, each release still needs to be assessed and checked before it's deployed. In locked down environments you don't want users installing stuff nilly willy, or have external sources push updates into your network. Mozilla still has an extremly long way to go on this front
And before you rant more about "competent administrators", FF requires a lot more administration than IE does and is a lot more fiddely to configure. I was on the ESR mailing lists for several months but then gave up on it recently when a dev (about 3 weeks ago, so extremly recent) posted Firefox is not an enterprise browser, and has never purported to be so.
I think FF should take a leaf from Google as to enterprise setups...