Speaking for myself, my "negativity" surrounding this news is based solely on the non-involvement of the score's composer with the title song. Which, I fear, could have a "negative" effect on the film itself.
I consider that to be a legitimate point of concern. But if some people want to label me a "naysayer" for expressing it, then so be it.
I'm still not getting why you've got these concerns simply because David Arnold did not get a songwriting credit. Some people seem to think that because he didn't write the lyrics, he has zero involvement, as if EON went behind his back and awarded the title song to someone else. Two things stand out in my mind:
1) Arnold is a professional musician. When it comes to deciding who gets the theme song, he has incredible power. Not only does he have legiitmate power because he's a part of the process, he's got expert power. He knows what he's doing; he's the most qualified person in the decision-making process. Babs and MGW are not professional musicians, so in that respect, David Arnold has more power than they do. While the decision may ultimately rest with them, they would be absolutely out of their minds not to listen to him. And while they've certainly made poor decisions in the past, they've also made good ones of late: hiring Craig, bringing Martin Campbell back, employing Paul Haggis, scaling back the involvement of Neal Purvis and Robert Wade, hiring Marc Forster and wanting to explore the emotional side of James Bond. They're clearly not out of their minds.
2) MK12 announced that they have completed the title sequence over a week ago. I can't imagine that as being a one-day job, so I imagine they took some time to do that. And at the absolute minimum, they had to know how long the title song was going to be in order to make a title sequence. It wouldn't look good if they made a four-minute sqeuence or a five-minute one when the song clocks in at four minutes and thirty seconds. Thus, EON knew how long the song would be. More, the title sequences often contain imagery relevant to the film:
GoldenEye featured Soviet icons,
Tomorrow Never Dies had information,
The World Is Not Enough showed oil and
Csino Royale's imagery related to casinos and Bond starting out in his career as an assassin. Even
Die Another Day had it: the title sequence featured imagery of Bond being tortured. So my bet is that MK12 heard the demo tape, or at least got to read the lyrics (though hearing it would be better). The press release about Jack White and Alicia Keys doing the title song came out six days ago, but nowhere did it say "they'll start recording next week". My bet is they've actually been in the studio making the song; it could well have been done for some time. With the flm's score usually being one of the last things composed because the composer often needs to see a cut of the film in order to match the score to the on-screen events, David Arnold is likely to have plenty of time to work
Another Way to Die into his score.