To be honest, I am not really concerned about this, since its a rather large framework (almost 150 classes, almost 13,500 loc) and (for us anyway) its the foundation of our applications. It really has to be reliable for us, so even if the tests took an hour to run that would be okay for us.
Nice in theory. Sucks in practice. More than one developer here (on a "must never fail on pain of death" project) has skipped running the entire 1.5 hour test suite because "their one little change" won't break things and their one little test didn't break. When you're in a hurry, one and one half hours can seem like a long time :)
Redundant tests are bad. They slow things down, they are more tests to maintain and they provide no benefit. You don't need to prove that 2+2 == 4 more than once.