I saw Alchemist play about a dozen times between 1994 and 1997. They were pretty good live, a mix between thrash, death and psychedlic stuff.
Most of the good aussie bands are long gone though. Back in the day we had excellent metal bands like Christbait, Necrotomy, Damaged (they are still around but they suck), Corpse Molestation (turned black metal), Anatomy (also turned black metal), Blood Duster (still around but they suck too), Entasis and Sadistik Exekution.
These days I only pay attention to Earth and Frankenbok. Aussie alternative bands are pretty good though....