I came across the following paper describing a usability study of Mailvelope, a browser addon implementing OpenPGP.
The abstract of the paper is
This paper presents the results of a laboratory study involv-ing Mailvelope, a modern PGP client that integrates tightlywith existing webmail providers. In our study, we broughtin pairs of participants and had them attempt to use Mailve-lope to communicate with each other. Our results shown thatmore than a decade and a half afterWhy Johnny Can’t En-crypt, modern PGP tools are still unusable for the masses.We finish with a discussion of pain points encountered usingMailvelope, and discuss what might be done to address themin future PGP systems.
Interestingly, I had not heard of Mailvelope before I came across this paper. So, that was a welcome find as well…!
The paper also describes suggestions to improve usability of PGP clients. Somebody interested might want to contribute.