Still working on Test::Aggregate, but so far it works well. Currently we have tests which would normally take 13m25s running in 4m17s. I call that a win.
Regrettably, this might kill Test::Class adoption for us. Test::Class also runs the code in a single process, but the inherited tests push the test time up to an unacceptable level. This is disappointing to me as I would love to convert almost all of our tests over to Test::Class. It's one of the best test modules out there.