The Union Pilot
Should help you make to decision to join the union. Good funny site for whoever made it and actually makes some valid points.
My theory on unions has always been that unless your permanantly employed ( actually have a job to protect ~ opposed to being contract or casual ) in a reasonably large organisation alongside other other union members your wasting your money.
Unions in my opinion choose not to bother chasing small time operators which is probably where you'll be starting your career.
The latest AFAP news letter amongst other things had 3 examples of them helping some employees get their entitlements back. The employees worked for a Qld Aero Club, Moorabbin Flying School, and NT Company. All sounded like small GA organisations to me.