Dave Larsen asked me on Twitter where I stood on the "faith in Jesus"/"faith of Jesus" debate but realized 140 characters might not do it. Frankly, there's no silver bullet so several books wouldn't do it. Here's the skinny on my thoughts.
1. First, most probably don't even know what we're talking about. In a number of key places in Paul, the literal expression Paul uses is "faith of Jesus Christ," even though most translations thus far have translated it "faith in Jesus Christ." Rom. 3:22; Gal. 2:16, 20 are a couple for starters.
2. I believe that in most of Paul's discussion in Rom. 4 and Gal. 3, as well as verses like Rom. 3:28, Paul has human faith in view. These are not places where he uses the expression "faith of Jesus" but speaks of faith in general as the mechanism of justification. However, such faith is primarily directed toward God, not Jesus (e.g., Rom. 4:17).
I disagree with Wright that faith is a "badge" of membership in God's people for Paul. I wrestled with this for a good long while. What is Wright saying? He's so smart and deep. As has happened with many such things I have struggled with, I finally decided the problem was not that I was stupid but that Wright (in this case) is just wrong. He's a Reformed Anglican and Paul isn't. Faith is a mechanism of justification for Paul, despite later debates about monergism, synergism, etc.
I might add, however, that I agree with Wright on many other things.
3. Romans 5:19 and Luke Timothy Johnson gnawed at me for a good long while. The language is almost exactly parallel to Romans 3:22. Obedience of one man is similar to what the faith of Jesus would mean. Many will be made righteous is pretty much the same as to be justified (same exact word). Strangely, 2 Corinthians 4:13 pushed me over the edge and I have an article in CBQ about it. The train of thought makes most sense if Paul there speaks of our faith imitating the faith of Jesus.
4. So my hunch is that the "faithfulness of Jesus" was a tradition of the earliest church coming out of Jerusalem. Paul seems to use the phrase, "through the faith of Jesus Christ" in a formulaic way, as if he is presenting tradition. And my sense of the development of early Christian soteriology, the topic I started writing on during my sabbatical, sees this phrase as corresponding directly to the earliest understandings of Jesus' death--the death of a righteous person that satisfies God's wrath toward Israel and thus catalyzes Israel's redemption from enslavement. As Philippians 2 puts it, "obedience to the death," the "faithfulness of Jesus Christ" that is an atoning sacrifice. On that half I agree with Hays.
5. But I agree with Dunn that Paul quickly moves to our faith... in God though more than in Christ. Paul does have a place for faith in Christ in his theology (e.g., Rom. 9:33) but it is subsidiary to faith in God. I've argued that he may exploit the ambiguity of the phrase "faith of Christ" to move from what traditionally referred to Jesus' faithfulness to his emphasis on the necessity of our faith.
As I put it in the article, Paul moves "from Hays to Dunn," "from faith to faith." This is a very complex argument and unprovable, but it makes sense of all the data in an elegant way, in my opinion.