Creating reporting applications in AJAX is often more challenging than developing data entry CRUD applications. Reporters usually need to process lots of data, preferably on the client side to minimize the amount of information that goes through the wire. Reporters need to know how to apply formulas, group the data, and calculate totals and subtotals. Add to the mix a requirement to give the end user an ability to customize the look and feel of the report, and you're facing a serious project.