My experience is that it isn't necessary in the F series, i have the F11 myself...awesome camera all around.
That said, I also just picked up the image-stabilized Panasonic TZ-1, and am stunned...in a good way...at how well the I.S. works. In fact, speaking in point and shoot terms, I'd say once you get to the 5x+ zoom factor (not an issue with the Fuji f11) then I.S. is important.
The solution for me is to have two pocket cameras...a dayzoom and a night. In the day the Panny TZ-1 cannnot be beat by any other pocket camera, I'm having the most photo fun I've had in many years. But at low light, I can't be without my f11...it's smaller, does amazingly well in lower light. So, I now get 95% of my shots clear as a bell by having these two cameras. They both can be had for about $300 each or less...not bad at all.