I have 4 windows open and firefox is using exactly 96908k. Heck, states remote is using 65000 or so.
If you were seeing high CPU usage, it was very likely that you had either a corrupted plugin or a similar issue. I have never seen firefox go to 99% without a defective plug-in of some sort (adobe reader version tend to hang, but they do the same thing too in IE).
Enjoy Opera, I guess. FF isn't an issue here.