Two meta-notes:

1) I'm not comparing to the JUnit core code, so it's quite likely that at some point, I'll ask for a change in code that I originally wrote, and you merely faithfully copied over.  My apologies in advance.  Always feel free to point out if a request will take a long time proportional to its benefit.  Especially...

2) Since this is such a big check-in, and github is not 100% ideal for reviews of long code snippets, I think in many cases, the right thing to do will be to add a TODO on this pass-through, and then address them soon later.