I'm still using Excel 2003 at work. It does all we need it to do.
And at home, Open Office's Calc is so compatible that I can forgo Excel completely, although I still use the Excel Viewer.
But there are some really neat features of the latest Excel. I especially like Data Bars and Color Scales.
To learn more about them, I studied this Excel Tutorial from Udemy.
Some of the other tutorial sections were helpful, too. For example, Pivot Tables have been updated. What used to be Page Fields is now Filter. And unlike Page, Filter allows you to choose more than one value.