This was all trivial in 2007. In 2010 I can't get the AllItems.aspx view to use my DisplayPattern.
This is the outline of my site column definition:
<Field
Type="Computed"
Name="Test"
DisplayName="Test"
Group="Test"
ID="{9D7643FD-3D46-231E-8425D-5250C7524521}">
<DisplayPattern>
<![CDATA[hello world]]>
</DisplayPattern>
</Field>
The "hello world" text is shown in the display form, but not in AllItems. Has something changed here?