Actually, both the camera and the flashes have indications. They will indicate that the flash fired OK and there is a different indication for the flash firing at full power but the camera still didn't think it was enough.
Now that you mention it, I'm not positive how the camera handles the flash in aperature priority mode. I'll check on that, but I don't think it will force the the shutter any faster than the fastest flash sync speed (1/125 for the N80). A good thing to check though before I start.