Intelligent auto is simple and convenient, it just turns your camera into a fully automatic point and shoot.
Superior auto is much the same, but permits the camera in some situations to take more than one exposure and composite them in an HDR like scheme. This won't work if the camera or subject is moving.
One fellow says the auto-iso feature is all but useless without an ability to set a minimum shutter speed to go with it (true if you use aperture priority, maybe it makes sense in some other mode).
Tom's Digital Photography Info / tom@mmto.org