I'll go ahead and use this question as an opportunity to explain why I get involved in these protests at all (SOA, OWS, NATO, etc), what I contribute, what I get out of it, and what I deem as achievements. Here goes:
The answer to your question depends on what you mean by "this protest". In my experience, as a participator and observer in large-scale protests (such as the NATO summit protests or Occupy Wall Street), there are at least three classes of concurrent protest that I can identify:
1) The collective protest - whatever it is that the entire group is rallying for or against. In this case, the NATO summits.
2) Individual and/or smaller-group protests:
Both the NATO and Occupy protests have been criticized for not having central or identifiable complaints/messages. This is largely because these protests are bringing together people who represent and/or are protesting such broad and disparate issues including (but certainly not limited to) drone warfare, imperialist foreign policy, corporate manipulation and corruption of politics & currency, immigration, women's rights, labor; Code Pink is there, along with Voices For Creative Non-Violence, SOAWatch, Veterans For Peace, labor unions, ethnic and racial advocacy groups, 9/11 Truth-ers, Ron Paul supporters, etc. All of these organizations (and many others which I can't presently remember) have their own agendas and issues that they are protesting or advocating; and then there's always the anarchists who basically protest everything.
3) My own personal motivations for participation:
Typically, I participate in protests just to be physically present (in solidarity with the classes listed above), to be a witness. This was the original reason that I sought out OWS on September 17th last year; when I realized that it was so much more than just a protest, I decided to stick around. My other motivation and ultimately my primary contribution to any such protest is to make a whole lot of noise. It's what I do for a living, so I figure I might as well lend it to whatever causes I deem worthy. Plus I've found that protests tend to be appropriate forums for "Protest Songs." Thus my contribution usually consists of original or cover songs performed with guitar, harmonica, and/or vocals; but I'll also do "instrumental" stuff - clapping, clanging, whooping, whistling, drumming. At one point down at OWS they had these long shofar-type instruments. They were fun. And loud :D
In many demonstrations there is also what I would call the programmed protest, where the agenda unfolds from a stage. This class of protest seems to take precedence at the SOAWatch vigils and it was the cornerstone of the Rally to Restore Sanity and/or Fear. It's not really relevant in this particular instance or in answering your question, since such a thing was not really central at either the NATO demonstrations or in the Occupy movement more generally. But I mention it to illustrate again that there are many different layers to these protests.
In any case, I'll assume that your question refers to either the first or third classes mentioned above - that you are either asking:
What did the (collective) NATO summit protests achive? OR
What did YOU (Gio) achieve by participating in this demonstration?
To the first question I simply answer: I don't know and I don't care. I believe that there's value in direct action, whether it achieves anything in the end or not. What did Yeshua achieve in throwing the tables in the temple? Did the money changers suddenly stop their practices just because this lunatic stormed through, causing mayhem? Probably not. But there was power in the act nonetheless. At least I believe there was.
So in Chicago, just outside the NATO summit meetings, tens of thousands of us from all over the country and the world demonstrated non-violently for three whole days, causing some disruption in and around the city and voicing our discontent with systemic violence, war, exploitation, corruption, and so many other evil things. We locked arms in the streets and confronted police repression and violence with peace signs drawn; with dance, song, march, chant, smiles, laughter, and so many other beautiful things. This, in itself, is an achievement.
As for my own personal achievements - I accomplished exactly what I had set out to do. I acted in solidarity with thousands of peace-seeking brothers and sisters; I was a witness to the weekend's events and I can speak to what transpired with clarity, honesty, and presence of mind; most importantly, my guitar accompanied me for much of the festivities and when my guitar was too burdensome, I was usually otherwise contributing to the cacophony (though there was also time for quiet meditation, prayer, and even a group yoga session at a lovely park in the city).
In the end, I find that it's not so much about what I achieved in reality - or what I could have achieved or would have achieved if I had done anything differently. I was never so deluded to believe that NATO would shut down, or Guantanamo prison, or the hundreds of US military bases around the world, or the war in Afghanistan. That was never my aim, though it would have been a very cool result. My sole aim was - and essentially always is - to bring glory to God by being the best person I can be (that is to say - the most badass) in whatever particular place and time that I find myself.
It just so happens that I planned for that time and place to coincide with the NATO summit protests in Chicago on May 17-20, 2012. And I am indeed proud of how I spent my time there and all that we accomplished together, working toward a more peaceful and just world.