What is the benefit of using GAT versus implementing patterns

This might sound like a newbie question to you and it is. But what is the the advantage of using the GAT package if you are already implementing the patterns in your projects. Plus if you have a project layered out and already in development what kind of benefit I can expect by switching to GAT also how to implement GAT to a mature project

As we all know, first rule for any business is profit. So my question is what is the profit of using the GAT I am just interested. Maybe you know about a webcast that will go over the benefits of GAT.