Well, if we get to choose, I'd choose a fast lens with IS
I totally agree on wanting a fast lens as it can help you catch action (which IS isn't helpful with), but what if I want to take that lovely wideangle prime hiking with me to get some nice landscape shots? The fast lens does me no good when I need to stop down and shoot at f8. Even on a wideangle, IS would be useful at a slow shutter speed...even if it was less necessary.
For me, the more options, the better
. That is why when I was shopping for my 70-200, I decided to save up so I could get the 2.8 IS...sometimes the 2.8 is the most useful, sometimes the IS is, and sometimes it's both.