I don't think we're discussing Australia anymore, but we do have a bicameral system in place as well. The Upper House is elected through PR and the Lower House through STV. Your vote is never really 'wasted' (unless you draw those genitals on the paper) but we've still ended up with a "you MUST be either Left or Right" situation. While there are other parties that can sometimes hold crucial seats, it typically boils down to just two parties dueling it out.