I write many custom controls and think that the HtmlTextWriter would benefit
from a method such as:

writer.Write("<td>{0}<td>", new HtmlTextWriterCallback(this.WriteCell))

void WriteCell(HtmlTextWriter writer)
{
   writer.Write("Some Content");
}

This is a simple example but for html templating of a site this would be
very efficient, useful and cool.

Thanks,

Mike