I'd see it as a bonus rather than an absolute must: the wider you go, the longer time times you can hold without a stabilizing. And at a certain point, you can't get much slower. The nice example posted by Virtual Rain only works because the shot is (1) fairly wide and (2) the people standing at the reception desk (this is where your eye is drawn to) aren't moving much. At such slow shutter speeds, the subjects motion becomes at least as important as camera shake. Even when you're at 1/30th of a second, people should move fairly slowly or better, stand still or pose.
Regarding Tokina lenses, their UW lenses are superb, the 11-16 mm f/2.8 is the sharpest crop UW zoom on the market (beating both Canon and Nikon in optical quality and mechanical quality). I find the zoom range limiting, so I opted for the 12-24 mm instead. I'm very, very pleased with it. The build quality is very high and I'm very happy with the optics as well. The 16-50 mm f/2.8 is also very well constructed, but it's not as good as Canon's or Nikon's 17-55 mm lenses.