The upper lip will always hurt regardless because it is the most innervated area. As for the rest of the face it depends upon these factors;
-Use of Anesthetic Creme
-Power settings (how much zap)
-Hair density
-Thicker hairs absorb more laser energy=hurts more
-Operator skill, consider tipping
-Brand of Laser used=the Lumenis Lightshear Laser covers the most area per shot, only one pass, uses suction to decrease pain
-Victim's level of pain tolerance

Not to mention the bite out of your purse or wallet, but hey...you'll like the way you look...