I think it's worth it. Take a day off school! But more importantly, you get heap and heaps of notes on that day. The main problem is that you need to read them ALL! The people who do the talk are examiners who knows the stuff well. They tell you what is expected of you in the exam.
I went last year. And I can tell you it is worth it. Definitely helped me to achieve a band 6.
Good luck people. Hopefully this year we can get more than 2% of people in Band 6.