Rhys,
Since Printable String doesn't include the ampersand, I think it
is a relatively poor choice for an organizational name, although it
is one of the choices under DirectoryString. Teletex, aka T.61, seems
to be much more flexible, especially when/if the nonspacing
diacritical marks and secondary characters are supported.
Personally, I would rather see a string format such as Teletex
used which includes support for all of the Western European
languages, at least, than to continue ad hoc hacks such as including
(a) for @ signs. Yes, it may work within certain contexts, but it
is just extending bubble gum and bailing wire workarounds.
Bob