Flock is based on the Firefox codebase, but the company has added several social features that leverage social networking accounts. The bookmarks, for instance, are your del.icio.us or magnolia bookmarks. If Firefox makes those features standard, that's great for Firefox users, but it closes the niche that Flock has exploited.
In any case, a Flockbot posted a comment on that blog post quickly, saying that Flock was still in the game. And here we are a few months later. I've heard nothing about Coop, but I can say that the new Flock 1.0 private beta is in very good shape. It does everything that Coop promised and more.
Rather than write a long review, let me just point you to the TechCrunch review:
Flock 1.0 Beta Released: Surprisingly Very Good
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