But one thing that stood out was .only(). In every major testing framework IT'S ASSUMED the dev is going to want to run one test at a time (sometimes). They make it super simple: you throw a ".only()" on the test, and the test runner only runs it.

In Node, you instead need to pass some special command line flag or add .only to every describe above the test ... which just makes a basic operation (run one test) much harder than it needs to be ... for zero benefit whatsoever (again, just do it the way every other test runner does it).