I'm ashamed to say it but yes I have smacked my oldest daughter a few times, its always been as a last resort, when I've tried every other means to disipline her and shes still being naughty, but it makes no difference, its wrong to smack a child, and I still feel so guilty now even though the last time it happened was Christmas.
I've been reading self help books and I've discovered 'Ignore bad behaviour, reward good behaviour' and it really works, well atleast for us anyway.
Oh by the way, when I say I've smacked her I just mean a single slap to the leg, I've never beaten her.