In Piper's lastest "Fresh Word", he has written some tough comments about Wright's view of justification.
"The other book is a response to N. T. Wright on the doctrine of justification. I have no immediate plan to publish it until I get the feedback from critical readers. My motivation in writing it is that I think his understanding of Paul is wrong and his view of justification is harmful to the church and to the human soul. Few things are more precious than the truth of justification by faith alone because of Christ alone. As a shepherd of a flock of God’s blood-bought church, I feel responsible to lead the sheep to life-giving pastures. That is not what the sheep find in Wright’s view of Paul on justification. He is an eloquent and influential writer and is, I believe, misleading many people on the doctrine of justification. I will keep you posted on what becomes of this manuscript." 
[HT] Justin Taylor's blog