I used polarizers a lot when shooting film, on digital the filter often seems to cause loss of contrast even when the lens is well shaded. Mine are all multicoated, but I suspect a lot of reflections come from the polarizing foil sandwiched inside the glass which is not coated, which interact badly with sensor or filter stack in front of the sensor.
I'm very happy using polarizers on lenses much wider than 28mm, I regularly use it on my AI 20/3.5 and I'd like to try one on my AIS 16/2.8 fisheye. My rule is this: if it improves the image use it, otherwise leave it off. Doesn't matter which lens/focal length. Sure you can get a dark band in the sky when using very wide lenses, but whether it shows depends on the angle of the sun and lens ... for example if the sun is very high the band of maximum polarization runs near the horizon all around, which is fine by me.
