Now tha David Miliband appears likely to quit politics the undoubted front runner for the post of Shadow Chancellor is Ed Balls. He has shown himself to be a surprisingly effective communicator and would undoubtedly be better than any alternative candidate at harrying the government.
There is one small flaw with his candidacy- his position on the economy is that the coalition policies are doomed and we shouldn't stop spending until some unspecified time in the future. If he turns out to be wrong, as I suspect he will be, then Labour will find themselves in an untenable position and will all too easily be painted as an unreformed tax and spend party still addicted to Brownenomics. Even if he turns out to be right the government will get the blame for any double dip anyway, regardless of whether Labour supported the policies (look at how Labour emerged unscathed by Black Wednesday).
Labour chose the wrong leader on Saturday but that mistake would be less serious than appointing the wrong Shadow Chancellor and therefore the wrong policies in the current climate. It would be a tactical masterpiece and a strategic disaster.