One annoyance however is that when you export your Numbers spreadsheet to Excel it will include a table of contents explaining how your sheets and tables were converted worksheets. While this might be helpful, it's not likely to be appreciated in a business environment.
So here is how you get Numbers to not include the table of contents when you export to an excel spreadsheet:
Simply edit your com.apple.iWork.Numbers.plist file in ~/Library/Preferences to include an additional key called "EEDropTableOfContents" and set it to TRUE.
From Terminal you can simply type
defaults write com.apple.iWork.Numbers EEDropTableOfContents
-bool TRUE
To edit it as an XML document you need to run
plutil -convert xml1 ~/Library/Preferences/com.apple.iWork.Numbers.plistthen add an entry that looks like this:
<key>EEDropTableOfContents</key>
<true/>
Or if you use Property List Editor included with the developer tools it will look like this: