On Mar 1, 2010, at 1:37 AM, Dan Davison wrote:

> Carsten Dominik <carsten.dominik@gmail.com> writes:
>
>> :-)  I should have known.  These days, babel is the answer to most
>> questions ... :-)
>
> Well, that wasn't the conclusion I meant to be drawn -- I thought the
> pure org solution was best here! (at least for simple summation)

Well, yes.  But the pure Org-solution is not predictable.  If you turn  
on formula debugging,  you see that Org computes this: