Regime change in Iran is a good thing.
It won't happen because of this though. They'll throw a hissy-fit, realize they can't really do anything about it, but better abide by the 'don't pursue nukes' stuff anyway because you've got Trump & Netanyahu as a double-act rather than Obama & Netanyahu at each other's throats.
Rouhani looks like an incompetent due to the deal imploding, probably loses a lot of internal influence with the religious poobahs, hardliner might get positioned in power next time around. Yet said hardliner's still in a bind and won't do anything stupid because they're not completely insane.
And that's all worst-case scenario. Best-case scenario there's some new deal/agreement reached. And the most likely eventuality is something in-between those two things happens, lots of blustery rhetoric & eventual saving face and backing down.