Is there any documentation or example how to use MvcContrib.TestHelper.Ui and WatinDriver?
I haven't found any real documentation for it, but there are examples of its use in the source code for the CodeCampServer project. You might also want to take a look at Chapter 20 "Full System Testing" in the book "ASP.Net MVC 2 in Action." It's a really great look at a similar approach to what the WatinDriver is trying to accomplish. Its discussion is also great in terms of designing your UI/HTML to be testable with tools like WatiN, and techniques to help make your browser testing less brittle.
EDIT: The WatiNDriver in use in the Code Camp Project source code isn't technically the one from MvcContrib.TestHelper, but I'd be surprised if it differs by more than 2 lines of code. Basically it looks like they borrowed the code directly from MvcContrib and added some of their own stuff on top of it.