Three thoughts:
1. Much of the criticism of OWS is of the "this is not enough" variety which is really not very helpful. The powerful Seattle demonstration against the WTO in 1999, supported by many labor unions and environmental organizations, was not enough. Having a million people worldwide demonstrate against the US attacking Iraq in 2003 was not enough. Electing a Democratic president and Congress in 2008 was clearly not enough.
Of course, none of these were enough. We're facing a gigantic juggernaut of corporate, government, military, and media power and it is difficult to overcome. If it were easy, we would have already won. So just saying it is not enough is no more helpful than saying it sucks to get old. Yeah, so what?
2. Much of the criticism from political insiders is that outsider action doesn't work. And outsiders (like OWS) criticize political insiders because Washington clearly doesn't work either. What history has shown is that outsider/insider strategies work the best. Outsiders to push the limits and ensure the insiders don't get corrupted/co-opted and the insiders to actually make the changes happen. JFK and LBJ were pushed by the civil rights movement and JFk/LBJ provided the federal troops and pushed through the legislation and funding that helped make it all work. Liberal media publicized it all. It probably wouldn't have worked without all these components.
3. After years of creating, attending, and supporting street demonstrations, I'm always wary of a protest when I don't know who is behind it or how it is organized. Every demonstration attracts flakes, true-believer radical vanguardists, selfish thugs, crazies, sociopaths, and undercover police provocateurs. Demonstrations need to have some way of overwhelming these disruptive/useless/dangerous people with mass numbers of regular, goodhearted people OR weeding these folks out OR at least having some way of preventing them from doing very much harm. Otherwise, the demonstration will be hijacked off to some weird place or another. In the past, leaders like Martin Luther King provided guidance and a voice for the media to get good quotes. Organizations like labor unions have provided discipline and large numbers that helped keep bad things from happening.
The nonviolent anarchist movement also has mechanisms (small meetings, decentralization, media spokespeople, and more) that can also serve the same purposes, though are sometimes not sufficient. It appears that, so far, OWS has been able to stay on track, create a pretty good vibe, attract support from unions, community groups, and others, get (and create) good media accounts, and keep moving forward. I hope OWS continues and can provide a good outside force to push the political inside game to a better place.
But there is plenty of space in the world for someone else to build a progressive movement using other methods. OWS isn't stopping you. Go ahead and do it.
I first posted this here - at the end of a waning discussion, but I spent enough time writing this that I thought it should get a little more attention, so I copied a slightly different verson here.