More generally, manipulating FF's about:config settings would be nice, I guess.

You can set about:config settings using the FirefoxProfile class in WebDriver - hopefully
as the code-bases merge, this will appear in RC soon (though it may already be do-able
somehow)

The 1.x API is frozen, so we won't be adding additional methods to it. Fortunately,
it already has the functionality to use a "template profile", so you can use the FirefoxProfile
class from 2.x and call "layoutOnDisk" on it to create the template.

Marking this issue as fixed, as the required functionality is present.

This isn't very portable, making it unusable for writing tests that will be run by many
people in different locations, unlike having the ability to set a parameter in the
same manner as the host name, for instance:

<parameter name="selenium.locale" value="en_IE"></parameter>

Being able to set the locale as the above example would be much preferred, and from
the returns from my Google search, would help a lot of people.