Just yesterday Mozilla released version four of Firefox, bringing with it a new UI and many changes under the hood. It looks and feels a bit like Chrome, but without losing the customizability that has always set it apart from other browsers.
The most noticeable change over Firefox 3.6 is that everything is so much more responsive, and pages render very quickly. The Features page on Mozilla.com lists some fairly impressive V8 and SunSpider benchmarks, which Download Squad says are slightly better than Chrome’s results. It seems like Firefox has finally caught back up to the competition, and hopefully will remain in contention thanks to the more frequent release cycle Mozilla plans to move toward.
The new “App Tabs” that you can pin to the left side (much like the Faviconize Tabs extension) are nice, as well.
The complete list of user and developer features is available in the announcement.