The following paper was presented at ABZ'2014 last week, and is now available in the conference proceedings:
Newcombe,
C., Why Amazon Chose TLA+, in
Abstract State Machines, Alloy, B, TLA, VDM, and Z Lecture Notes in
Computer Science Volume 8477, 2014, pp 25-39;
http://link.springer.com/chapter/10.1007%2F978-3-662-43652-3_3
I'm happy to provide copies privately on request.
regards,
Chris