I think you missed off one of the most important points profits and sales also shot up. Here is a quote:

"sales skyrocketed after the announcement, and Gravity Payments continues to take on new clients at a rate it never had before. It reports nearly doubling profits in a year, from $3.5 million in 2014 to $6.5 million in 2015"

I think most companies will be looking at the sales figures with more envy. There could be a lot of reasons for it - good publicity and PR from the salary rule, happier and more productive employees etc.

This is a great feelgood story but we will need time to see if it truly works long term or if it really was more a result of being good PR. I'm sure other companies will follow their example and give it a try and in turn give us more data to work with.