I'd believe that more if it hadn't been getting consistently worse over the course of the last five or so releases, if not longer. Leaks were listed as the fourth bullet point on the 1.5.0.1 release notes, right below "International Domain Name support for Iceland (.is) is now enabled." No offense meant to the four people who were clamoring for the Icelandic support, but memory leaks that cause me to have to restart the browser multiple times a day seems a little more important. Also, the leading quote of "I don't know how often these leaks were severe enough to cause noticeable slowdowns or thrashing, but enough Firefox users seem to care about memory leaks..." doesn't inspire confidence in their concern. They seem to think that this is a theoretical problem.