I use higher ISOs in my Trip all the time, but not for the same reason. I use it for low light, not for increased shutter speed. For my purposes it's easy--load whatever film you want, then estimate what aperture is needed in your particular lighting situation, knowing that the shutter will always be 1/40. My most commonly-used ISO in the Trip is 3200--Delta 3200, Neopan 1600 pushed, Tri-x pushed.
My street photography is probably different from yours, but I do not find MY movement to be an issue. Unless I'm taking photos of breakdancers, 1/40 is frequently sufficient--again, I'm not the one that's moving, I stay still and take the photo. I'm also pretty sure the camera defaults to 1/200 whenever possible--I think most P&S cameras do to avoid camera shake--so with ISO 400 and f/2.8 you'll probably get 1/200 in most daytime lighting. If full sun is f/22 1/200, there are maaaany stops of light to go down before the camera would switch to 1/40.
Mike, I've heard of your "pointing at the sun" trick but am not understanding the second part of it. How would the shutter still be at 1/200 after you move the dial off A?