Great thread - I've been riveted to the news following the crisis of the last few weeks and wondered why there'd been no MN discussion. Turns out you were all here 
It seems clear that if austerity continues in Greece the country will continue to have a fairly unpleasant time of it. Conversely, my sense is that no-one really knows what would happen if Greece either left the eurozone, or left the EU altogether. To me, the elephant in the room is the political dimension to the whole sorry mess: the ideological commitment of many within the EU's governing institutions to irreversible political, fiscal and economic convergence of EU nations. Were this commitment not so deep, Grexit could surely have been considered some time ago, and managed perhaps with less pain than Greece has already been through. But leaving aside the economics (which I have seen argued convincingly both in favour of and against austerity within the existing political situation) the ideological commitment to the EU and to the eurozone makes this impossible.
There is good evidence that the eurozone was always intended as a political mechanism, to force greater fiscal integration between eurozone countries in the service of 'ever closer union' and - eventually - a United States of Europe. That's why they seriously considered creating a currency union without fiscal union in the first place: because the belief was that over time the necessity of fiscal union would become obvious, prompted most likely by crises like the one we are currently witnessing. So, then, the choice is between relaxing the ideology (eg by allowing countries to exit the eurozone, by easing up on 'ever closer union', by being in any way politically flexible) or forcing an entire country to its knees and leaving pensioners weeping on the streets outside shuttered banks, in the service of proving the need for greater centralised EU fiscal control. Guess which way the EU has jumped.
Ultimately this isn't about an economic 'right' or 'wrong' decision. It's about whether at the last count it's the elected governments of EU members that are in charge of their nations, or whether in fact it's the EU supranational government that calls the shots. To my eye if they are to have a united currency, the answer has to be 'It's the EU, silly'. Otherwise you end up with situations - like the Greek one - where governments are democratically elected on fiscal promises they can't deliver, because in order to maintain overall stability in the currency union the fiscal levers are controlled by umbrella institutions that don't answer to the Greek people, at least not enough to make them care about any Greek 'democratic mandate'. It follows from this that something has to give: either national sovereignty (ie democracy) or currency union.
I think Tsipras has grasped at least one end of this, which is why he keeps going on about democratic mandates. However (unless he is playing a very crafty and mendacious game indeed) his insistence that Greece will still stay in the eurozone means he hasn't grasped the entirety - ie the reality that staying in the eurozone means that Greece gives up on democratic self-rule, at least where fiscal policy is concerned. Either that, or he's lying and is trying to force the eurozone to dump him, so as to ensure the best possible terms of an exit.
Personally I think the best solution is probably a managed Grexit. I think where fuckups have become this entrenched, the best solution is to let the chickens come home to roost, deal with the pain and rebuild. But I fear this won't happen, and what will emerge from the wreckage will be a eurozone as ideologically single-minded as before, with the peoples of its various nations more restless, more frustrated and (in the case of Greece) more impoverished than ever.