I was getting very strange behavior on a project using external interrupts, so I investigated it further and ended up posting this thread:
http://arduino.cc/forum/index.php/topic,59217.0.html
I think a note in the Reference section about attachInterrupts() would be helpful for users. It would make the interrupts behave as expected rather than have an interrupt occur based on something that happened before the interrupt was attached.
Near the end of that thread there is a solution given to eliminate the unexpected behavior. For now, I think a short note with the small patch code would suffice.
Others suggested that the attachInterrupt routine itself should be altered to include the fix. This seems like a good idea in the long run.