We're saying the same things, just in different ways. I was attempting to be humorous in my previous comment, preferring comedy to precision. :)

Interestingly, I have also had some experience with teams that have very high test coverage, but which don't refactor consistently (or effectively). These teams also do not seem to benefit from dramatically improved performance. My current theory is to write tests to support refactoring and don't worry about any of the other benefits.

That's something I had never considered. Do you have any general guidelines for testing for refactoring?