Senator Durbin has stated that progressives forced the hand of the rest of the Senate Democrats and caused them to agree to a public plan with an opt-out provision. Olympia Snowe finds this "deeply disappointing," but I do not believe 60 Democrats should cater to one Republican.
Apparently advocacy works, but the political battle has not ended. Even though many articles have portrayed the public plan as a "done deal," the vote has not taken place yet. Furthermore, the conference committee process will produce any final version of the reform package.
Warning: Read the fine print, and carefully watch the proceedings after things go into conference committee. Liberal elements of legislation vanished during conferences earlier this year (e.g., forceful limits on executive pay).