I don't even know how many committee meetings I have been to, either as a student or supervisor. Every place does them slightly differently and there is usually substantial freedom in the format and tone. Some include a formal presentation, written report before hand, or both. Others are a casual conversation.
As fas as I know, however, the point of having a committee meeting is mainly to get some constructive "outside" guidance on the work you are doing and have planned. Lot's of other things can come out of committee meetings, but making sure you don't have your head stuck up your advisor's ass is a key component. In most cases, a committee comes on board once you have a research plan in place and meets once or twice a year.
Based on this, I was surprised to read Algae Girl's post about her first committee meeting happening at the end of her third year. In a follow-up post she mentions she may be defending in December, indicating that her first committee meeting is happening at the 11th hour of her degree. Any input from the committee at this stage would, by necessity, be window dressing.
I have to say that I'm a little surprised a degree program would be set up that way, although it could just be how things fell for her. In my department, the committee needs to be established and a research proposal needs to be submitted to the grad school, no later than the end of year one. The committee has to sign off on the proposal and often has a meeting to discuss, including a presentation by the student. A considerable amount of feedback is given to the student at that time, which hopefully improves the overall research plan.
What do you see as the point of committee meetings, at least as they are intended (I've been to some useless ones)? How early and often are the done at your institution?