The --() with comma format of the function operates faster than the () * ()
format. Just thought I'd throw that in as added information.
If you have just a few 'special' SUMPRODUCT() formulas in a workbook it
probably doesn't affect performance a log, but if you have hundreds or
thousands of them, then using the SUMPRODUCT(--(),--(),--()) format could
have a performance advantage over SUMPRODUCT(()*()*()).