In short: it’s incredible! While I haven’t had the misfortune of working daily with Ansible playbook runs that take in excess of tens of minutes, I’ve still felt the tedium of even waiting for a simple 3-4 minute role to finish doing its thing. Now the entire thing takes around 50 seconds (about 250% faster) and the process of iterating on several changes is no longer such a bore.
The only downside I’ve personally come across is that this magnificent speed improvement does not extend to ad hoc commands, so something like
ANSIBLE_STRATEGY=mitogen_free ansible 'group1' -m shell -a 'reboot' is still bound to take as much time as prior to installing Mitogen, though I’m far less concerned with improving such executions.