To start with a very solid base in your organization, what would be the main thing you have to look for to make an Apptio Implementation successful?

Is it the Available Information (Updated, Correct, Complete)?

Is it the Compromise of the entire organization?

Is it the Technical Skills for bulding quality reports?

or Effective Comunications between StakeHolders?

Others?

At a high level, alignment from IT and Finance leadership. It is a must to have to leaders from these groups on board. I also think TBM should be in IT but partnering with Finance. After that it is knowing/understanding cost centers, IT Towers / Data, and modeling. Within each of those layers you need partners with skill sets to help with the tool (Cost Centers you probably need Finance to lead this, IT Towers and Drivers should be someone from IT or multiple people from IT,  and modeling would be TBM. I would also consider someone in IT to help in the model area but not for Apptio modeliong but for automated data pulls from sources.Hard to say what is the most important, they are all needed. I think you can run cost center and IT Towers at the same time but you should wait to model until those categories are clearly understood. Another component is communication...to the business, to IT, to Finance...to everyone. A governance program is a must. 

Oh...and alcohol helps a lot too!

Having a clear, well defined, sponsored first use case to solve for helps a lot. Combined with a longer term vision of the "real" value TBM delivers. In my opinion it is a catalyst to maturity.