[mikewarot]

I'm not willing to completely count it out, mostly because quantum annealing seems to be a real thing. D-wave is based on this.

The classic example, though, is factoring large numbers using Shor's algorithm. In order to do this, you have to rotate qubits many times at very small angles, which would instantly be wiped out by noise. I doubt Shor's algorithm will ever work for large numbers.