To add to what Stefan has said, I would set the right indent somewhat left
of where the leader stops. If the leader stops at half an inch from the
right margin, I'd set the indent to at least 0.75", maybe 1".
The drawback of the \w switch, of course, is that it is not practical to add
tab characters to centered headings (though those are often the ones for
which you omit numbering).
But I'm curious, Stefan: Did you test your text-with-tab with the \w switch
before adding a white character after it? It's been quite a while since I
wrote
http://word.mvps.org/FAQs/Formatting/TOCSwitches.htm, but apparently
when I was experimenting with TOCs to write that article, I did not find any
need to add text after the tab character in the heading provided the \w
switch was used. This may have changed from Word 97 (which is what I was
probably using when I wrote the article) to Word 2003, however.