I'm curious about this as well. Does anyone have any experience with this? It would be interesting to hear someone's opinion since CFEngine seems to have been around for awhile.
cfengine2 is a simple and effective mechanism for managing systems. However, cfengine2 has some issues. It has limited facilities for abstraction, resulting in a lot of code duplication. It has no built-in template engine, meaning that if you need to assemble a file based on various conditions you have to cobble it together with pattern matching and line-insertion. It's pretty easy to screw this up and lose idempotency. There's a 30-package-install limit per cfagent run, which fails silently. This is very annoying and requires some hacks to circumvent.
Also, in cfengine2 you have a configuration file that's basically <classname> : <list of hosts...>. If you approach more in terms of <hostname>: <list of classes>, it's a minor inconvenience.
Cfengine3 addresses some of these issues, but I haven't used it much so can't really give it a fair review.
CFEngine spawned Puppet spawned Chef (rougly speaking)
I never got involved with BCfg2 or lcfg so I don't remember the history behind.