Great

To my experience Question & Answer anti-spam, is a great method to reduce spam. I hope it will do so on my new WordPress site too, as I received a awful amount of comment spam already (before installing this plugin).

Although the current description says “Compatible up to: 4.1.4”, so far it seems to work great on WP4.2.1.

Only improvement I can think of is a possibility to have multiple questions, of which one would be shown at random.