I asked the exact same question last year:
Its in this thread:
http://vcenotes.com/forum/index.php/topic,1642.0.htmlI joined last year for a fee of around $200 last year...
This year its only $99 and I reckon that's a bargain!!!! I already renewed for 2009 last year.
What I got out of it?
Discounts from certain food places in Union House, Computer use (where you can go on any website you like without being restricted) at the Student Union Computing Centre, access to the Rowden White Library (members only ...you can borrow Japanese manga and DVD's there..this library is sort of like a pop culture library where there is nothing academic-related in that library) and discounted memberships to some clubs and societies on campus.
There's also a special member's only lounge in Union house. I've personally never been in there until someone pointed out to me near the end of last year.
I reckon its worth it.