Quote
In this paper, we show that the polynomial scaling of SA (Shor's algorithm) is destroyed by input errors to the QFT part of the algorithm. We also show that Quantum Error Correcting Codes (QECC) are not capable of suppressing errors due to operator imprecision and that propagation of operator precision errors is sufficient to severely degrade the effectiveness of SA. Additionally we show that operator imprecision in the error correction circuit for the Calderbank-Shor-Steane QECC is mathematically equivalent to decoherence on every physical qubit in a register. We conclude that, because of the effect of operator precision errors, it is likely that physically realizable quantum computers will be capable of factoring integers no more efficiently than classical computers.
I don't see any published rebuttals in a quick Google Scholar search. Maybe there will be a breakthrough (or already has been... any QC wizards listening here?) in handling the fuzziness of quantum calculations as you scale up the number of qbits, but 256-bit ECDSA looks pretty darn secure to me right now.