Upgrade from AA 2006 SP2 MP2 to Agile 9 Questions

 We are contemplating an upgrade from Agile Advantage 2006 SP2 to Agile9, however we have heard some pretty conflicting stories regarding the conversion, learning curve, and performance moving forward.  We have talked to consulting companies, and end users of the Agile9 system.

Some consulting companies say that there are no issues with the upgrade, everything goes really smoothly, and some end users say that Agile9 takes away as much as 40% productivity and that more people would need to be in the system to manage a lifecycle which originally took 1 person to manage.

What I am interested in is a "no suprises" document which clearly illustrates a fair account of issues and resolutions during the upgrade process.  I've read the whitepapers and marketing documentation which in the real world doesn't really answer my questions.