[gruez]

>I’ve literally had someone sit in front of a Linux computer with OpenOffice and work fine on it until they realized “hey the title bar says OpenOffice Calc - it’s not excel! I don’t know how to use this!” Despite the fact they were using it just fine.

I guarantee that this won't happen with "brenda in accounting" (ie. typical excel jockey). The mismatching shortcuts/formulas/feature set will immediately tip them off. For someone who's viewing a few spreadsheet and/or doing some basic editing (ie. entering cell values), I can imagine it happening.