Having an employer want you to sign an AWA is a bit like your employer telling you that they have a new superannuation plan mark XII for you.
When you ask what was the matter with the old super scheme they tell that the new one is a lot better but the reality is that it is better for the employer.
If the employer is in a hurry for you to sign it get legal advice as Coral said....No one in their right mind would sign any contract without legal advice...