Comparing Memory Usage of Firefox 2 vs 3
That's a bogus argument. Virtual size is absolutely unimportant as far as the performance is concerned. You have a fixed amount of memory in the system and if Firefox takes up a lot of real memory, other parts of the system will feel the pain. The fact that the *real* memory usage of FF 3.0 is low means that it is not being greedy about using system resources. Every process has the full VM size to play with, so looking at the VM size doesn't really tell you much about what effect that process will have on the rest of the system.