John Piper's Ambiguous Doctrine of Justification

I found this critique of John Piper's doctrine of justification by faith at the Contrast blog on Wordpress. You might find it interesting. Piper is quoted as saying:

Present justification is based on the substitutionary work of Christ alone, enjoyed in union with him through faith alone. Future justification is the open confirmation and declaration that in Christ Jesus we are perfectly blameless before God. This final judgment accords with our works. That is, the fruit of the Holy Spirit in our lives will be brought forward as the evidence and confirmation of true faith and union with Christ. Without that validating transformation, there will be no future salvation.