In some of the branches auditing is always one of the top requirements. This topic is always subject to lot of discussion. Do you really need it? Does it influence performance are the regular questions.
In 3.0 we usually offered add-on by C360 as the solution for auditing. A few days ago I read the post on the Microsoft Dynamics CRM Team about business auditing. And this makes the world a lot easier :-)
So check out this post at their side if you like to have your own "free" auditing.