Now introduced the ability to reveal all formulas with one click
How to access what’s new:
When editing a spreadsheet you can enable this view in three ways: Select the ‘Show All Formulas’ button on the top right; Select ‘Show All Formulas’ in the View menu; Click Ctrl ‘ (Cmd ‘ on a Mac.)
For more information:
http://docs.google.com/support/bin/topic.py?hl=en&topic=15115