The Iran deal may fall apart. Is this a good thing?

The "deal" stinks. We gain next to nothing. Iran is quite capable of cheating. They will have their assets unfrozen and are free to resume global trade. They will utilize the newly freed funds to buy arms from Russia and others and deliver them to Assad and other bad actors.
This deal is a gamble of very serious proportions. If it works, it will be a coup. If it fails, it will destabilize the area in wildly unpredictable ways.

On the political front, sustaining a veto might just lead to some stuff getting done, instead of protecting the White House.

That would depend on who you are asking. A few things it did not accomplish, the release of our four American prisoners being held or their IBM stock pile. And will it really prolong the capability of them obtaining a nuclear weapon. They tell us it will but can we really trust Iran. I don't buy into the argument that they couldn't do anything for the prisoners. Iran needed the sanctions removed that is a main reason they where at the table. The G5 + 1 had all the cards. And I believe they fell for the buff by Iran. And now we have the deal that we have.