Firefox 3 Beta 4 is about to be released (later today or tomorrow), as the twelfth milestone, in what already is the longest development time for a Firefox version since the initial Firefox 1.0 back in 2004. Fortunately, Mozilla has not been shy to set as many milestones as needed, and given the many new features and tweaks Firefox 3 introduces, it seems anything but sensible, specially considering it’s not only about Firefox but Gecko, the web page rendering engine and the Mozilla platform as a whole which affects the many products based on it.
Firefox 3 gets several performance improvement gains. Among them, profile guided optimizations (PGO) provides an optimized Firefox build based on the way it internally works. So far it is only available for Windows. Linux should follow shortly and Mac OS X could also make it before final release.