I'd like to suggest that @tab be replaced with @| in a multitable.
I have two usability objections to @tab. First, it is long--four
characters. When you have a wide table to typeset, having "@tab"
between every column makes it less likely you'll be able to fit
one row on one line of your text editor. (Makes you wish for the
simple "&" of LaTeX.)
Second, "@tab" contains a word, which makes it look more like text
in the table than a formatting command. This visual overlap makes
it harder to grasp the sense of a multitable source at a glance.
@| is already used in Texinfo as a heading part separator, so it
seems a reasonable choice here.
(I don't really like "@item" in multitable, either, but I don't
have a good suggestion for a replacement.)
