All the time. I go through phases where it's worse than other times, but it's always there a little. I'm usually pretty good at knowing who I can swear in front of and who would be offended, but when I'm in my heavy swearing phase, I'll sometimes do it in front of someone like my boss or my grandmother. That's when I know it's time to back off a little. I wish I was as colorful with it as my brother -- he was in the Navy for 12 years, and learned to swear quite brilliantly. But I'm more white-bread about it. I just use the words you got in trouble for looking up in the dictionary in 4th grade.
EDIT: As far as swearing AT people, I've been known to cuss my brother to his face, rarely to anyone else -- unless I'm inside my car and the offending party is in another car who just cut me off in traffic. Then the barrage of language out of my mouth would offend a longshoreman.
_________________
AS: 136/200
NT: 66/200
EQ: 45/50
Go as far as you can see. When you get there, you will see farther.