Depends
It all depends! Some of the lectures have the HSC markers for the subject and some have normal teachers! What it all comes down to is the lecture's ability to talk, present their info in a creative and interesting way! Cause a few times, they have had good info, but have simple lost all attention from the students because of their boring nature!
Well thats my opinion, and I am greatful that I have gone to some of these lectures and I have goten quit a lot from them!
If you are willing to attend and pay %100 attention I suggest you go! Otherwise you would be waisting your time...