Right now we don’t have to have plugins to any particular configuration system, but obviously I do prefer Cobbler because it’s better 
Razor to me feels like a research experiment because I very seldom want to choose what I want to install based on hardware class and often want to purpose machines based on need with different machines all being installed to the same hardware class.
That being said, if it can support Chef, I’m sure we’re fine with it too.
I also haven’t seen many people using it in production – by comparison, Cobbler rolled out the international DNS system across ~20 different data centers.
Basically setup with a bare metal system is nothing more than provisioning an SSH key in kickstart or preseed post (super easy).
(AnsibleWorks is also working on a really cool callback system so a newly brought up system can phone home and request instant configuration, this will require our server solution)
There are already in the plugins/inventory directory a inventory plugin for sourcing inventory from Cobbler, and also a bunch of other cloud systems. Ansible is pretty friendly in that if your inventory source is a directory you can pull from multiple inventories (bare metal + cloud + other cloud + INI file) all at once
and talk to machines without caring about where they are.