Distinguishing Berman and Midkiff
Both Berman and Midkiff, according to Justice O'Connor, "directly" achieved a public benefit, making the fact that the property was turned over to a private party immaterial. By contrast, the benefits in Kelo were only secondary--"increased tax revenue, more jobs, maybe even aesthetic pleasure." Since virtually every taking that attains some sort of assembly gain can provide these secondary benefits, the Court's holding today does not realistically exclude any takings.
So the distinction here is that removing blight (Berman) and fixing an oligopoly (Midkiff) are fine, but economic development through rejuvenating a dying area (Kelo) is not a public use. I don't buy it.
Justice O'Connor is, in my view, splitting hairs. She's caught once again in a situation where she has no formal answer to the legal question and makes unconvincing arguments. The Public Use Clause needs to either be more than just rationality review of the legislature's determination (which O'Connor alludes to when she says that the current protection is no more than that already afforded by the Due Process Clause which prohibits irrational legislation, but would make it hard not to overrule Berman and Midkiff) or this issue is not what should be making eminent domain decisions.
It's not at all clear what the Public Use Clause originally meant, whether it was intended to limit permissible takings or whether it was just describing the types of takings for which just compensation must be paid. I admit to not yet having read Justice Thomas' dissent that discusses the historical meaning of the Clause, but I've read contradicting accounts from equally viable sources, and there is, I think, no concensus on what the Clause originally intended.
And the Public Use limitation is problematic anyway, because as long as you're willing to allow the retransfer in some situations (such as the bilateral monopoly problem), the Court has to be in the business of checking the legislature to see if this project is really going to be profitable, really produce the kind of benefits the developer is claiming. There is no reason to think that this is something the Court is good at.
We've talked on Ex Post before (e.g. here) about the Just Compensation solution to this problem and how to both disincentivize these condemn and retransfer schemes by making them more expensive and more adequately compensate takees for subjective losses. That is, takers should have to share the gains they receive from the assembly of multiple parcels with the takees. We have, admittedly, all stolen this from Tom Merrill, as argued in his Kelo amicus brief. But this, to me, is the way IJ should be fighting eminent domain abuse and not by making Public Use arguments.