The register form I already have on the site (before the plugin you suggested) already prompts the user for email, confirmation of the email, a first name, a short description of who they are, a password with confirmation.
I installed the first plugin you suggested, and re-enabled registration. and now after adding the first plugin you described they have to answer yet another question.
Not personally, no. I simply grabbed reasonably looking reg plugins that looked like they might do the job as examples. You may have to to do some further searching and testing to find one that suits your needs.
That's what led me to recaptcha and the useless plugin I already have that challenges the user at registration.
On my sites, I usually switch all registration off unless I have an overwhelming reason to want people to join as subscribers.
That's fine for you and it's generally rude to invalidate the concern with "well I never use it"
That's not addressing the issue.
That said, http://wordpress.org/plugins/stop-registration-spam/ looks interesting/
I don't need "interesting", I need fixed.
Customisable Q& A challenges certainly work a lot better than captchas - especially if you change the question relatively frequently. I'd be surprised if there weren't a couple of other plugins like this lurking in the Plugin Repo. The ideal plugin, in my opinion, would be one that displayed a random Q&A challenge from a bank of questions that you had previously created and could customise.
A solution to this issue is not hunting around for plugins that "maybe" will work.