Err... I just opened up Excel (2002 since that is all I have at work), selected a cell, clicked on the SUM button (sure it uses the mathematical symbol for sum but if you hover over it, it says SUM), and then was able to click and drag (or CRTL + click for nonconsecutive cells) to select cells for the sum. This is all via the GUI. I'm not sure how this is hidden. Heck, I did this in a Japanese version of Office which I can't read.

Is this different in Office 2010 or any of the newer versions of Office? I mostly use LibreOffice and even there it has the same "all GUI" functionality.

Do you think 2% of Excel users (or 10%) use Pivot tables? Do you think Excel would be the massively powerful tool it is today without that?

Same for scatter plot, import csv files delimited with % marks, and the ipmt() function?

Humm .... I don't believe that just the presence of an "Advanced" button somewhere in the settings makes a software hard to use. May be FF usability experts do. :)