Here are some of Watson's primary conclusions:
"Whether they think in terms of 'faithfulness' or of 'faith', the prophet and the apostle are at one in their assumption that emunah or pistis refers to the human response to the divine promise of definitive, eschatological saving action. The apostle's message is "gospel", in which human speech is the bearer of "the power of God unto salvation" to those in whom it evokes the response of faith (cf. Rom.1.16). The prophet likewise seeks to evoke a response in which the entire life of his reader is reoriented towards the future divine saving action of which he writes. His book begins with a despairing question about salvation: "YHWH, how long . . . shall I cry to you, 'Violence!', and you will not save?" (Hab.1.3) . . . From beginning to end, the book of Habakkuk is concerned with salvation . . . And it is concerned only with salvation . . . It is not concerned, for example, to address the problem of unrighteous conduct among the covenant people.
When Paul cites his proof-text in the form, "The one who is righteous by faith shall live", he shares with his scriptural source the conviction that all human life is to be lived in the light of God's final, comprehensive act of salvation. For Paul, the prophetic "by faith" entails the corollary, "not by works of law"; that, and not an explicit christological refernce, is the point he seeks to establish on the basis of Habakkuk 2.4, in order to bear witness to the radical priority of divine saving action even over the human action enjoined in the law itself (162-63)."
A chapter truly worth a careful read!