Michael Bird, the prolific NT scholar and one of two bloggers at Euangelion, points out that the disagreement about the so called "New Perspective on Paul" can be summed up as a disagreement between "those who want to read their Bible's historically and those who want to read the Bible theologically." He writes:
The difference is between those who say (1) "my authority is Scripture and I am willing to affirm a Confession in so far as it coheres and comports with Scripture"; and (2) those who say "my authority is Scripture as understood by the Confession". These are not the same thing. The second position is not "truly reformed" and it treats the Confession rather like the Mishnah of the Rabbis or the Magisterium of the Roman Catholic Church.
The tasks of systematic theology, then, are subservient to the tasks of Biblical theology. Or as Bird puts it:
BUT, Systematics cannot demand that exegesis and historical study conform to its system. Theology may be the "Queen of the Sciences" but she is a puppet Queen sustained by the strings of exegesis and by the hands of biblical scholars.
Of course, the relationship between the two may not be quite that simple.