We do extensive CWP using XML. Have been for a few years. It requires a solid understanding of the browser environment, including scripting languages such as JavaScript or VBScript.
This is not for casual HTML users as Lasso allows for, it is more like real software development requiring an understanding of the browser environment, its document object model, and the XML document object model. If those are new concepts to you, there will be a learning curve. In our case, the learning curve was well worth it.