Interesting comparison, but shoukd be mentioned that Dell, AWS, and others, are leveraging knowledge around Chef.

And Citrix, Rackspace and Oracle are using Puppet ("leveraging knowledge"? pls no).

Appeals to authority don't tell us anything about the technology except that somebody we've heard of is using it.

Dell and Amazon leveraged chef to help build Crowbar and Opsworks respectively. Crowbar ... leveraging ... get it?

In any case, noting Opsworks is based on Chef is not an "appeal to authority".[1] That knowing Chef means you have a head start on AWS's official devops tooling, seems a relevant data point for a comparison. (The officially supported devops tooling leveraging a particular CM system is different from simply being able to be managed by a CM system.)

As for Rackspace, here's the CM category of their dev blog:

  http://developer.rackspace.com/blog/categories/configuration-management/

And here's "How Rackspace Uses Chef to Deploy OpenStack in the Private Cloud":

  http://developer.rackspace.com/blog/cooking-with-chef4.html

Quoting a different Rackspace article from Feb 2013:

The Rackspace Private Cloud Certification team sought out and tested a number of bare metal provisioning tools. While there are a number of excellent tools on the market, none seemed to fit quite well. On one hand, some tools were all-encompassing in scope and would try to provide an end-to-end solution. On the other hand, tools were too narrow in scope and provided a solution for a specific operating system or did not provide an appropriate amount of flexibility.

Eventually, we picked a deployment model consisting of a combination of tools that would provide the right balance of features and flexibility. We chose the Razor provisioning engine, combined with the OpsCode Chef configuration management tool.

1. http://plover.net/~bonds/bdksucks.html