What are the main differences between MS Excel 2007, 2010, and 2013?

The main difference I personally noticed between2007 and2010 is that the formula functions are easier, in2010 - When I add various resultant cells to a final summation at the bottom of the page, I merely can type +A1+next (look for the cell) + next (look for the next cell, but upon pressing "+" the cursor does not return to the cell address I am in; but rather waits at the last position +1st Next. 

Hope you can understand what I mean there.

Other differences:

• In2010 if I merely time =sumif(............. I will come up with the prompts of what the operators I need for this formula to work, then I merely push "Tab" and the ) is added and the formula is inserted.
• Calculation, graphing tools, pivot tables, and a macro .... In early versions of Excel these programs were written in a macro language
• 2010 vs2007:
  • Improved ribbon icons
  • Loop error messaging
  • Data filter functions easier
  • Improved pivot tables
  • Improved conditional formatting
  • Improved add-in functionality between other Microsoft platforms
• 2013 vs2010
  • I like the "running ants"
  • New analytical tools 
  • Excel2013 notices pattern in the user's data entry and then auto completes the remaining data
  • Formatting easier
  • Paste format paint bush can be clicked once, then click click click everywhere you want that format type

I AGREE WITH MISS BONNIE ANSWER  

There are more commands and group of commands added inside some ribbons and tabs, for example the sparkline group is added in2010 and it is not found in2007.

The version changed and the options gets more wider than before like going inside a huge box of elements related to used work.

They got easier in the new one but changed the method which needs more updated training to the latest steps or trying until you get the point.