In the OP: they dont have a Tester. They just load it on their MacBooks and presume it works for the other 95% of the world
Really, wordpress.org users are the testers, wordpress.com users are the customers. I'd love to hear what the OP now recommends though, that would provide some good perspective.
Tons of free software projects have ESTABLISHED testing procedures. Have some of your developers/project members sit and check it is OK before shipping it.
Even more so, if you have a huge company and PAID developers on the project (Automatic).
Really, wordpress.org users are the testers, wordpress.com users are the customers. I'd love to hear what the OP now recommends though, that would provide some good perspective.