To make an educated decision on upgrading to Excel 2003 or not, check out this list: What’s New in Excel 2003

Personally I’m a fan of the XML and List functionality.

For a good time, check out the confusing animation from MS on upgrading to Office 2003, depicting office users with dinosaur heads.

For a great post on the latter, check out Steve Rubel’s: Microsoft Office Marketing is Stuck in the Prehistoric Era