In the past, Flock for Mac OS X was based on Gecko, the web browser layout engine from Mozilla that powers the Firefox browser. Unfortunately for Mac users, Flock was a bit on the slow side.
Flock 3.5 for Mac OS X has replaced the Gecko engine with the shiny, speedy new Chromium 7 engine, which is based on WebKit. I downloaded the new Mac OS X edition yesterday and it feels much faster than the previous version, although I have no benchmarks to validate that claim.
Flock is unique among web browsers in that it has a scrolling sidebar that contains a constantly-changing flow of updates from your social networks, including Twitter, FaceBook, LinkedIn, Flickr, YouTube, and RSS feeds. To log into all of the social networks and services, Flock requires a free account. Once you have logged into the Flock account, all of the updates start to scroll down the sidebar. It's a great way to keep up with your social networks while browsing or blogging.