I run my testing as part of building, get minimal output, then have to look in the test*.log files for the details.  Seeing the output cluttered with lots of "gosh gee willickers, it turns out we think two is two - who'd have guessed ? " messages makes it harder to see what's actually gone wrong.  Of course, having lots of "aargh, I can't find some keys that I don't actually need" messages is even worse, but I gather that's getting fixed ...
Of course, when part of a test has failed, it can be helpful to also see the details of the parts that passed as well, but when a test has passed entirely, I prefer to say nothing more than "Pass."
Still, if more voluminous output about passing tests has helped find problems in the past, do as you feel is best.