I've long been accustomed to setting up servers one-command-at-a-time with SSH. I tried Chef and some of the others, but they seemed too complicated to get setup.

Ansible's out of the box experience allows you to start with some simple but useful constructs then allow you to graduate to more and more complex usage.

I started with some of the one-liners here, then setting up inventory files, then roles, some simple tasks and then (what really sold me) was templates.

Even just having those configuration files in an SCM is a huge win, but I honestly squealed with joy when I was able to write a nginx configuration file that dynamically included backend servers given a particular role. And that provisioning a new backend server took a couple minutes and was automatically added to the load-balancing proxy! (not to mention was instantly sending metrics to a graphite/statsd backend because collectd was installed automatically too as part of a common role and configured to point to that log collecting server!)

Magic!