The memory problem is pretty serious. I've been using the Memory Restart addon (https://addons.mozilla.org/en-us/firefox/addon/memory-restar...), which shows memory use in the bottom corner and lets you click to restart when it goes over a certain amount.
If I leave Firefox open during the day the memory goes up to 1.2 GB. The performance slows down at about 800BM memory. I have 8 GB so it's not a big deal but it still seems an awful lot of memory.