With the latest round of fighting around Gaza, Iron Dome appears to be a success. It intercepts somewhere between 75% and 85% of the missiles fired at Israel. I am not a military expert, but throughout history, missile-to-missile weapons were never that successfull. AFAIK (but would like to be corrected if wrong), other missile-to-missile programs were (relative)failures. Think Star Wars and the Patriot. US funded part of Iron Dome (IIRC), and the technology will be very usefull for the US army also.
Is this a game changer? I donot think so. The rockets fired from Gaza still disrupt Israeli civilian life, just like before Iron Dome. The difference is, the Gaza rockets have a much less success rate (I even think Pali rockets kill more Gazans because of miss fires, than it wounds and kills Israeli's). Israeli population still needs to go the shelters. And at the moment this is what the Pali cause is: shooting rockets at Israeli cities. After the unilateral UN bid for statehood, the Pali cause is marginialized, and they know it. They only thing they can do is shoot a rocket and shout "hey, look at us, we are still here". What I do see coming though is, with a possible next Israeli attack on Gaza, the Israel bashers, will shout now that Israel has no right, because Iron Dome gives already enough protection. Some will listen to this, so I think, if Iron Dome changes anything (besides the main point of protecting Israeli civilians), it is that it will ironically reduce somewhat support for military action against rockets fired from Gaza.
Thinking more widely, Iron Dome cannot intercept long range missiles, so while it might be able to intercept rockets from Gaza and Hezbollah, long range missiles from Iran cannot.