When the dust on all of this has settled and once Gordon Brown is consigned to history, Labour's NEC must change the party rules.
The ridiculous farce that has been going on in the last few days (and will probably continue) of a Prime Minister who clearly does not have the confidence of his cabinet or of his MPs but for whom there is no direct mechanism to get rid of him has to change. The Labour Party rules make it very difficult to remove a sitting PM if he/she does not want to go. I am not absolving the cabinet or the PLP from their responsibility here, if they really, really had the will they could get rid of him but their flaccid attempts so far have merely damaged the Prime Minister, the government and our country.
The Tories have a much better system for this sort of thing and Labour need to come up with something much better. They should also change their rules to ensure that any Prime Minister has to be elected by their party. Never again should a megalomaniacal bully be allowed to accede to their leadership unopposed.
If they want to be in government again in the future, they have to have a party constitution that will ensure the sort of mess they are now in can never happen again.