An example built using the AdvancedDataGrid is embedded below (it is a SWF file, requires Flash Player 9 for viewing):
Notice the tree view within a grid - that alone is a feature not found easily. On top of that, notice that there is a 'total' row in each of the categories of planets (click on the arrow to unfold a branch) - there are two aspects to this, first the summary (i.e. the total) is automatically calculated using a Collections API we have built, and secondly, you can specify a custom SummaryRenderer to display it any way you want, and in our case we are using column spanning so that it spans over the entire row. Now try doing that with your UI framework!
To understand what more you can do with AdvancedDataGrid, do read our writeup with lots of example code. Unfortunately, the live samples are not inline in the writeup (as we had originally written), you have to download them separately. You can also watch a video demonstration of AdvancedDataGrid. I hope this gives an inkling about the wide range of features and functionality in the AdvancedDataGrid.
Working on AdvancedDataGrid has been fun for me, mostly because of Sreenivas and Sameer, my teammates, who taught me most of what I have learnt about Flex.
And as someone commented on Ted's post featuring AdvancedDataGrid:
OK, the workflow and the code enhancements were nice, but not enough to get me excited. But now I totally want to get my hands on that AdvancedDataGrid!