The Mozilla team continue working to make their browser even better. And now Firefox has grown up to version 15.0.1; and naturally it enjoys some fixes and innovations carried over from the 14.0.1, yet also bringing some of its own. Some bugs (concerning sites being stored in cache after Private Browsing mode) from the previous release have been fixed; at the same time, some new ones have appeared, which are to be dealt with by the developers later on.
Compared to the previous version, Firefox 15 has a lot of new features: support for the SPDY networking protocol (reduces page loading time), WebGL enhancements (allows GPU acceleration for physics and image processing and visual effects in the browser), support for compressed textures for better performance, localization in Maithili, and silent background updates. All these have contributed to the already implemented full-screen support for Mac OS X Lion, auto-completion of typed URLs in the Awesome Bar, and other features carried over from the version 14.
While localization features are focused on a very specific group of people, WebGL enhancements, support for the SPDY protocol and optimized memory usage are beneficial for all users, as they are intended to make the browser work faster. Frankly speaking, it does feel being faster, even when loading multiple tabs.
However, it seems that the most awaited change is the background updates, which won't be distracting you from what you are doing in the browser anymore. In fact I didn't notice how Firefox updated to the version 15. I was just working as usual without any interruptions. This change is really enjoyable.
Unfortunately, there is still a lot of work to be done concerning the remaining bugs. Yet, the Mozilla team is working hard on making the browser more comfortable for the user, which is proved by the latest release.