And the memory leaks are ridiculous, even as system with lots of Ram will be brought to its knees by FF given enough time.
Except IE7 does "leak" memory like sieve, (it's hard to tell exactly what it's doing) at least in comparison to Firefox.
Consider the following link. It is by a well-known Mozilla developer, so while he may be biased you can be sure that a result that cannot be reproduced would set the tubes on fire some time ago.
I'm not saying that Firefox is the leanest application ever, but some of the charges against it here are incredibly overblown and of dubious veracity.