Do your own diligence on the hundreds of posts here about this problem but I would ask you to consider a few questions.
1. Ford says the hesitation/stumbling problem is normal, why then does Consumer reports include it as a bad thing in its reviews?
2. Many other brands have this transmission, do they all have a similar problem?
3. when cold weather hit new england, 2/3 of my problem went away. If it is normal, why did it go away ?