Stream is one of those plugins that I've always seen the potential in but it's never quite nailed it. I was a pretty big fan of Stream 1, and I wrote about my experience, but in the end it ended up logging too much and made the stuff I wanted harder to keep.
When Stream 2 came out and it was hosted by them, I had renewed interest. However, my migration to the hosted setup didn't go well and I ended up abandoning it altogether. Apparently, others also didn't always have a great experience — despite a stellar team working on it. Luke Carbis describes the Stream 2 failure in surprising detail within the Stream 3 announcement.
Stream 3 goes “back to the basics,” and the plugin is now self-hosted again, and it will be free moving forward. Stream will also now be part of XWP, the WordPress arm of X-Team — which I think is really X-Company, but either way it's a company of nice people whose overall structure never ceases to confuse me.
Luke calls the plugin, “akin to Akismet or Jetpack,” and I actually agree with him in regard to its potential. I'm certainly going to try it again now that it's on version 3 and self-hosted again. But I a bit concerned if it'll be able to be improved significantly now that it's free only and doesn't have a business model. Maybe as a free plugin on Github the contributions from outside folks will pick up to compliment XWP's work and it will become the really great tool I always hoped it could be.