InformationWeek's Scot Finnie has a few bones to pick with Mozilla's new Firefox 1.5 browser.  One of his main beefs is the fact that Firefox is still a memory hog.  I can attest to this fact personally as I have had problems with memory usage in all releases of Firefox:

Matt McKenzie, Editor of the Linux Pipeline, recently sent me a screenshot that showed Firefox 1.5's main process (firefox.exe) using 398,108K physical memory and 405,540K virtual memory - way more than is comfortable or necessary. And the number, he said, was rising while he was sitting there. On the other hand, on my system, a quick check showed Firefox 1.5 using about 27,000K on first launch, and between 50,000K and 60,000K after a couple of hours of hard use. That level of memory use is within bounds. (By comparison, IE6 used only 13,000K after initial launch on the same machine in the same session.)