As we should all know, it is the right of any nation on earth to pursue the peacetime use of nuclear energy to generate electricity. But since that same peacetime nuclear program can have military uses as well, inspection is needed. As such countries are supposed to work through the IAEA.
http://www.jpost.com/IranianThreat/News/Article.aspx?id=236771
And one of things inspectors look for is any attempts to advance the enrichment of Uranium to anywhere near the 95+ % level of bomb grade Uranium. And as it is, Iran is not advancing such Uranium beyond the about minimum 3% needed for reactor fuel. The second thing inspectors need to look for is the type of reactor designs. Some types of reactors, the like Israeli type, are breeder reactors, that can produce plutonium useful for bombs in its spent fuel rods. Other type of reactors produce only small amount of material in its fuel rods. Since Iran is not building its own reactors yet, that becomes a as of yet a moot question. Then there are questions on who controls the spent fuel rods, if Iran agrees to turn them over to a third party, Iran will never become a nuclear bomb power.
But now that the unfettered inspection question is on the table, IMHO, there is little possible reasons not to lift the sanctions on Iran.