Who's using this now, and if you're one of them, how happy are you with the module as it is?
FWIW, I recently commissioned Thomas, the Google SoC developer on simpletest project, to write a suite of tests for the organic groups module. Those tests will be available by end of month. I'm pretty happy with the simpletest framework in Drupal. I might be biased since I wrote it though. The Google SoC students did a great job extending it. And the simpletest project itself is magnificient.
We have thought about using simpletest for Drupal contrib modules that ship with CivicSpace.
great idea. start small. pick a simple module and write a few tests. No need to think of this as a huge commitment. But embracing expensive processes without the
backing of the Drupal community is really difficult. So if anyone is serious about using unit tests I suggest we start first with writing simple tests for core modules. Once these tests are shown to be useful by dev's to test their core patches, I think it will catch on with contribs.
these already exist, they just need some attention because so much has changed in recent months.