Have you used Function Points in Agile Projects?

Is you ask me, I will said: avoid the Story Points estimation. But, my approach is: I am using what best fits for the organization where I am working on. In my actual organization, people that not belongs to IT or software find Story Points a useful tool. So, what I did was put clear what Story Points meant (in terms of inherent error and subjetivity) which demands something like "evangelize" from month to all the organization, put clear the process and put clear all what will face for using them. In my case, for a chance of the destiny, I had the opportunity to interact with people that "created" Story Points method from the genesis so I learned from them all the "headaches" Story Points create on people that will use it until, as you mention, you mature on that which demands at least three initiatives. On the other side, I complemented Story Point with Barry Bohem´s Cone of Uncertainty to put clear what does mean the estimation we got into any iteration. Other important thing is: User Stories are not requirements. User Stories are only "an invitation to talk about requirements". That will impact the estimation.

Agree. Because of that is I made all the actions needed to clarify all related to User Stories and I record and publish all that happends around it to all the involved stakehodlers with the aim to made the process as better as we can in terms of the objective we need to achieve.