What sites do you have open JF?? wow that's the smallest ram usage for FF I've seen.
I had open this forum, one youtube video, a bank site that uses java, and the rest were mostly news sites or the such, with lots of flash and whatever.
This is with the browser being open for many, many hours and retaining all history and such.
Really, FF does not deserve the bad rep. Use the latest build, don't use any unnecessary plugs, and its extrmely fast.
It won't load as fast as IE or Chrome, but once you have it open there is no difference.
The Minesweeper builds are still considered unstable, although I agree there should be a supported 64bit version by now.