>> From an end-user's perspective, there's very little difference between "the task didn't work" and "the task worked, but took longer than your patience to wait." Both appear to be broken.

I disagree. Assume it usually takes 1sec but 1% of the time it takes 120sec. Does your test suite wait 120sec and fail 1% of the time or does it wait 1sec and speed up the test suite? These are test trade-offs IMHO