If I understand your situation clearly, you and your team know several applications well and have been testing the applications. Now you'll be directing user acceptance testing as well and need to explain what benefit you and your team can provide to UAT.
Let me share details of one of my experiences and then answer your questions more directly. I was in a similar situation once and worked directly with users through UAT. I was able to teach the users more about the application. Once the users were able to see more intricacies in the application, they became more skilled testers themselves and appreciated the testing team (as well as the developers) even more than they previously did. I gave them ideas and in turn I learned what quirks of the application irritated the users. I learned more about their perspective too.
I think there are multiple benefits, such as the ones I highlighted, as well as a few more. You'll get to know the users; they'll get to know you and your team. The users might be more inclined to share ideas that can add to your testing. You may also better understand what the users need to accomplish and become a better advocate for the users. I believe spending time with users of the products is beneficial.
This was first published in May 2008