What is your experience in adopting assessment for learning strategies?

What benefits do you see in assessment for learning?
What challenges have you encountered or anticipated?

(Definition of assessment for learning can be referred in the Feature Article by Prof. David Carless )
In the present issue, I collected six contributions involving a number of interesting practices and reflective thoughts. I am sure that there are many inspiring and interesting stories out there that I was not be able to include. Please share with us your experience or examples here.