Family Pack G and AP.O - Prerequisites to an R12 upgrade? Benefits of applying in advance of R12 upg

We are currently at the initial stages of analysing a R12 upgrade however our current application modules on 11i are in extended support and we are not on the latest support version of the code - which is Family Pack G. This particular query relates to Payables but also may apply to the rest of the family pack. We are entering the scoping stage for our Q4 2012 patching window.

The business needs to make a decision whether to apply AP.O or not. We need to know whether AP.O is a requried prerequisite ahead of upgrading to R12 or additionally if there are any benefits in terms of an R12 upgrade (days saved for example) from being on AP.O for our 11i system? i.e. what are the benefits of being on AP.O before upgrade to R12 outside of support.