Michael Horton makes the case that if by pietism it is meant that the supposedly pious are those who seek after immediate incursions of the Holy Spirit apart from the ordinary means of grace, often, if not always, marked by private, individual exercises and methods, then it is a piety that finds no ground in the Reformed consensus. Adjacently, if by confessionalism it is meant that the inward working of the Spirit is downplayed in favor of external and mechanical "going through the motions," as it were, with a concomitant minimization of the seeking after of godliness and growth in Christlikeness, then it similarly finds no ground in catholic Reformed thought and practice.
I find this reference particularly helpful:
"Writers like Iain Murray who speak of revival as the Spirit's extraordinary blessing on his ordinary means of grace stand in a long line of 'experimental Calvinism.' If revivalism is antithetical to 'the system of the Catechism' (and I agree that it is), it is nevertheless true also that confessional Protestants have often prayed for special periods of awakening and revival. Pro-revival Calvinists include the Puritans and the great Princetonians (Alexander, Hodge, and Warfield), not just Edwards and Whitefield. So the debate over the meaning and legitimacy of 'revival' is in-house. There is no historical justification for pro-revival or anti-revival Calvinists to write each other out of this heritage."
One may dare to ask, "Does this mean that the Holy Spirit does not always attend the partaking of the means of grace with His blessing, which then is the warrant for revivalistic clamor?" The answer lies in the humble posture that the creature must always have before the Creator. The Lord has promised to provide all our needs, and yet we are admonished in the Lord's Prayer to unceasingly pray for our Benefactor's supplies. Scripture assures us that the Kingdom of God will be unalterably consummated, and yet in the same pattern of prayer set before us, we are commanded to pray for its coming. The certainty of providence never precludes humble, heartfelt prayer.
Perhaps this debacle over "confessionalism vs. pietism" can best be resolved by keeping ever before us the doctrine of providence, in that God works through ordinary means and that the Creator-creature distinction will never permit the outmoding of prayer.