Everyone and their brother seem to be talking about Flock today, so I might as well throw my two cents in. If you haven’t heard, Flock is a new web browser based on Mozilla, for Mac, Windows, and Linux. The developers have a “0.5 Developer Preview Release” available for download. I’ve played around with it for a bit, and the browser itself seems pretty stable, but some of the extras are a bit buggy still. Flock is definitely a preview release and isn’t ready to be used as your full-time browser.
Flock does have (or will have) some cool tools integrated right in… like a blog editor, Flickr tools, del.icio.us syncing, and integrated feed support (like Safari). But, like I said, these extras seem to be fairly buggy.
I would say that Flock is off to a wonderful start. It definitely has a great deal of potential, once they get the kinks worked out.
TUAW is a more detailed write-up about it if you’re interested.