Here is another long exposure shot taken using the Singh-Ray LB warming polarizer. The water in this part of the Guadalupe river was flowing rather slowly so all I needed was about 1/2 second exposure to create the soft, flowing effect I wanted. I generally prefer to use a warming polarizer to avoid a blue cast in my polarized images. A standard CP is OK for the sky, but it makes the water look a bit strange.
BTW – I shot this image at f/22 and honestly couldn’t find any sign of softness caused by diffraction, even when pixel peeping the 100% crop.