So, after posting about my Firefox RAM experience I loaded up the latest stable Chrome, the latest stable Opera, and of course FF4. I loaded them each up with more tabs than I would ever use, each one in Identical order, and then allowed them to idle for quite sometime.
RAM Usage results:
Firefox 4 - 284 MB
Chrome - 312 MB
Opera - 345 MB
Which at least on 64 bit linux makes it the LEAST RAM hungry of the 3. I would also like to note that even Opera is using a very reasonable amount of RAM considering the number of tabs.
I will admit that FF3 was a pretty bad performer, and I, along with most folks switched to Chrome until the release of FF4. But today, with FF4 released, all of the major browsers performance are so close to one another, that it really negates performance as a bullet point when choosing a browser. Just pick your favorite in terms of UI, features, and extensibility, and use it. Right now the browser war is down to personal preference.