In reply to Tom Rizzo's post Bryant Likes questions why you would want to export a report to XML, and Tom provides a useful reply. I'd like to add how I found this feature useful too:
Lets say you have a report where, for the sake of readbility, you have indented some of the text, and you also have quite a bit of grouping going on. Lets also say you have a user who likes playing around with the data in Excel using pivot tables and all that kind of stuff, and to be honest, you would rather leave them to decide how they want to arrange the data rather than trying to get a fixed spec off them which might not then suit somone else's needs. If they export direct to Excel, they get the data arranged in the same grouping and indenting and they can't easily manipulate it. If however they are willing to do this in two steps (ok, you'll need to give them a bit of training) they can export to XML, then import in to Excel 2003 and they can pick and choose the fields they want to display, and where, because Excel can work out the schema all by itself (well, sometimes!).