This should get you started
http://www.google.com/search?hl=en&q=what%27s+new+inventor+10+2008&btnG=Google+Search
do your designs use Fillet Features? Inventor 10 didn't have Face fillets. Inventor 11 added a lot of new functionality. Maybe my favorite new functionality is 2008 (12) is something very simple Sketch Split, or maybe improved Contoured Flanges if you do sheet metal parts. If you do really complex stuff some of the new 3D Sketch tools...
And Loft with Center Line, and enhancements to Sweep. Sculpt certainly wasn't in v10. How did I ever live without Sculpt, and Trim Surfaces... ... a Boundary Patch that did more than planar surfaces, on and on.
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