This is, really, the only reason I don't use Firefox. And I keep trying to go back, probably every month for the last year and a half.
I do use a lot of tabs, but over time the memory usage grows to well over 1GB (sometimes 2 or even 3GB), and the memory is never released, even after closing all tabs. This has been a problem for me since at least FF 3.0, on several systems, each with its own unrelated profile. On both Mac and Windows. I don't think I navigate to particularly unusual sites.
I use no add-ons, at least on most systems.
The response to this problem is usually exactly the comments we see in this story, which are generally:
1) Memory leaks are due to bugs in add-ons. Disable all your add-ons one at a time until the problem goes away.
2) I don't have this problem; something must be wrong with you.
3) Just buy more RAM. It's cheap.
I don't understand why people are so aggressively against investigating these problems. Even with a task force announced to address the problems, a huge # of people in this comment stream are still calling foul.
I'm not sure if Chrome uses less memory, but at least when I close a tab, the memory is released. All of it. Immediately. I don't have to restart the browser to get it back.