The use of CLEF with WPMU plugins

I read the article about CLEF in the wpmudev blog and wonder if any of the wpmudev team have any experience of using CLEF alongside Membership Pro or Coursepress Pro? I've considered the benefits of two-factor authentication as a way of (1) beefing site security & (2) better protecting paid-for digital products from 'social' sharing. CLEF seems like the best option, but in practice I'm just wondering what experience is out there, given that my site has paid-for digtal products that are accessed by password.