While there is no guarantee that these talks will work (Obama himself has said they might not), it is better to try and fail then to not try at all. Besides, the Republican approach has proven so successful at preventing Iran's acquisition of a nuclear weapon! Note: I was being sarcastic.
Unfortunately, Republicans have now taken their objections and opposition of Obama's efforts to a whole new level. Today, a group of Congressional Republicans sent a letter to the leader of Iran "reminding" him of the U.S. Constitution and that any deal needs to be approved by Congress and that any deal is with Obama alone. They went as far as to say that Obama will be out of office in 2017 and that his successor could alter or back out of the deal with the stroke of a pen.
This is a new low for Republicans. Not only are they undermining Obama's efforts, they are also signaling that they would prefer war to peace. In saying that the next President could change the deal if he or she wants, Republicans have declared that we, the United States of America, are the ones to not be trusted and that we will do whatever we want regardless of our word. If these talks collapse in the coming weeks, I wouldn't be surprised if this move by Republicans will have been part of it. They have also all but guaranteed that a vote for Republicans in 2016 is a vote for war. How clear cut of a choice can you get?