As best I can tell, the device to which Ship is referring is not listed on Lex's site. All connectors listed
here seem to be Leviton connectors. I used to buy only
Bryant devices, easiest to built and lasted well, but now they are a part of Hubbell. I'm also a firm believer in the original being the best, I prefer
Union Connector pin connectors over all others. I, too, suffered through the "Harj-Lock" craze--my favorite was that the tension on the male cord entry had to be less than the female entry, so that one wasn't left with dangling, bare, live wires. Not sure how other locking connectors deal with this issue.
Ship, have you seen
Hubbell's SNAPConnect? Seems like it could be a labor savings for residential/commercial applications, but our industry doesn't use that many duplex outlets as a rule. Still, I suppose every second counts when one is paying $30+/hour, per electrician.