Love the hat! I use flash extensively since in Oregon the most of the year is dark and dreary.
Besides the typical shutter-flinching, none of mine seem phased by the flash, some even get excited and curious when the camera is out. I know some people in other species worry about flash damaging the eyes if you take pics during the first week of life (very young) but even then, I don't really worry. I've raised fancy mice for 4 years taking daily pictures from birth and none of my mice ever had any problems with it. Hedgies anyway have terrible eyesight and I don't think camera flash on a normal healthy hedgie is going to cause any problems.