Speaking of changes to display, it seems useful to easily *not* display units.  A lot of pages and templates put the units in a hyperlink, e.g. http://en.wikipedia.org/wiki/San_Diego has
    Area 840.0 km²
where km² is a link to Square_kilometre made with [[Square_kilometre|km²]] .

We can represent the attribute in SMW 0.4 as [[area:=840 km²]], but then the units appear as part of the value display.  To not display the units you have to repeat the number, [[area:=840 km²|840]] , which is prone to error.

I'm not sure what the wiki shortcut for not showing units could be. Maybe putting a trailing | with no space could only show the number.  Currently it falls through to chopping off "area:" as if it were a namespace, so you see
    =840 km²

Some number display is even more complicated, e.g. in http://en.wikipedia.org/wiki/Sun both the number and the units are hyperlinks:
    Surface area 6.09×1012 km²

the 6.09 part is a hyperlink to the http://en.wikipedia.org/wiki/1_E18_m%C2%B2 page that explains this order of magnitude.  This conflicts with the SMW tooltip that displays the area in other units.  I couldn't represent both at once in wiki source.

People are cramming a lot of info into those hyperlinks, it's almost to the point they need a context menu to document and link to attribute type, unit conversion, order of magnitude, units explanation, etc.