On API Names, Documentation... and... ExtractTemplateRows

The documentation seems reasonable except it leaves out an important reason for the existence of this property, which is what I was hoping to see in the answers. It sure does give away some of the answer to this quiz. Given that, let me also add this question to the quiz - what would you name this property so its name would be more intuitive, and you wouldn't need a long msdn reference topic in the first place?

I'd also love to hear what people are trying that causes them to ignore controls such as DataList and DataGrid/GridView and miss out on lots of (what I think) useful features by resorting to Repeater.

OK, first off to answer the question (as mentioned, the documentation on msdn does a reasonable job), but the key idea or the motivation behind the property is to be able to create tabular UI where columns align perfectly across rows (the browser does a real good job laying out tables), as well as to create DataList items that each contain multiple rows. Without the ExtractTemplateRows feature, you can achieve such layout, but its impossible to reliably align columns. You can sort of implement such layouts using Repeater, but you have to resort to HTML fragments for template contents, thereby losing any design ability.

For example if you want your items to be three columns, where the 1st column spans two rows, and the 2nd column in the 1st row spans two columns, you could use the following:
<ItemTemplate>
<asp:Table runat="server">
<asp:TableRow>
<asp:TableCell RowSpan="2">...</asp:TableCell>
<asp:TableCell ColumnSpan="2">...</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell>...</asp:TableCell>
<asp:TableCell>...</asp:TableCell>
</asp:TableRow>
</asp:Table>
</ItemTemplate>

This property is actually also personally interesting to me - its one of those properties that has existed since the early XSP/prototyping days way before v1 started to take shape. The feature was initially slated to be cut in fact, simply because there was no reasonable and short name to describe it... but I managed to save it... partly by simply leaving the code in there... The sad part about it is that it is limited to <asp:Table> and doesn't support <table runat="server" />. The latter would have made it designable.

On Repeater vs. DataList - I understand a lot of people choose the former for full control over rendering, or should I say percieved control. Sure, with the DataList you loose some control. But there are a number of style properties each with CssClass as well if you'd like, and we do in fact merge them logically (for example, the 2nd item picks up AlternateItemStyle followed by ItemStyle) that allow quite a bit of control over the rendering. In return for the abstraction you get all sort of goodies such as horizontal and vertical layout, fixed number of columns and wrapping (which by the way can't be done with CSS), separator items etc. etc. Also note that the controls work with plain IEnumerable, and optimize if they find an implementation of IList. You are by no means restricted to using DataSets. The whole data-binding architecture in ASP.NET v1 and v2 is based on being able to enumerate rows.