The new version Firefox 7.0 was released on September 27, 2011. This new version and release is part of Mozilla's rapid releases which started in March 2011.
Overall, there have been improvements and several thousand bug fixes since Mozilla started their rapid releases. This new version Firefox 7.0 boasts drastic improvements in terms of memory usage thereby providing speedier web browsing.
I've been using the new version Firefox 7.0 for a couple of weeks and have conducted some performance benchmark tests on Firefox 7.0 as well as Google Chrome.
Based on the tests, Firefox 7.0 performs better than its predecessor versions, however, it's still not comparable to Google Chrome's overall performance. The results of the peacekeeper tests are listed below. Please note that these benchmark performance test results will vary depending on various factors.