I know a couple of lads who went. Expensive upfront for skills assessment through vetass, expensive for visa (if enough points, plumber not on current skills in demand list), only get a provisional plumbing license and have to go to tafe (college) to upgrade, have to be supervised on a provisional and can't set up on your own without going to college to get your congtractors license.
Once you get there, there is not a lot of work and if you get a job, get a decent shovel as you will be using it a lot. Oh and its silver solder on copper, brazing!