Have they added HPR (aka HTD or HTP) type synchronous belts and pulleys? http://www.tbwoods.com/Products_Mechanical_Synchronous_Drives_SynchronousPlus.asp
Just curious, alot of people here, including myself, have been asking for the inclusion of these components in Inventor as far back as 2005. I'm still using IV 2011 but was curious, because this alone would make the upgrade worthwile for me.