Okay, firstly I don't know how much foreign aid we've agreed to send, as far as I've read that hasn't been discussed, so my assumption is that all money sent to Iran will be in exchange for oil.
Intel suggests Iran has all the materials and plants necessary to build a bomb within a few months if that was their goal. So the first thing I'd say is there is absolutely no benefit to sanctions at this point because it hasn't stopped them.
Now Iran has to dismantle its enrichment facilities, redesign its heavy water reactor, get rid of its enriched fuel, and pretty much undo a decade's worth of progress towards nuclear weapons before the sanctions are ever lifted.
This isn't Saddam kicking inspectors out of the country, and saying "Whaddya gonna do about it?" They don't get a dime of that sweet oil money until inspectors are satisfied.
Now we have the best deterrent of all in place, economics. Would Iran risk losing that cash cow again? Name a country so crazy it'd be willing to shoot itself in the foot like that. This is why all of your North Koreas and USSRs have to practice isolationism. Once dollars and cents are at stake, no one wants a nuclear war.
Could they cheat? I suppose, but the threat of instant sanctions snapping back (a provision of the deal) should at least give them pause.
