Yeah, definitely mood dependent! I do agree that saying it too often causes it to lose its meaning...kind of makes it taken for granted...
saying it and actually meaning it is not the easiest thing to do in the world. You want to make sure it's how you feel.
haha. i've only see jacky cheung once, in a video. so i would say the face. as for sek sau, definitely the hair and maybe the dimple(s).