I bought the Ethereal 1/8 Diffusion Filter Plus+ to add a small amount of softening/misting to my images under certain conditions. It certainly is a subtle effect and I might try the 1/4 version at some point. Of course you need to be careful with such filters as the effect is 'baked in' to the image, so I'm pleased this filter doesn't have an overbearing effect.
It's the usual quality you expect from Urth with its quality bezel to the easy-clean optical surface. I always check Urth for my filter needs. I sometimes wish they'd do a range of filters for black and white film photography, but I've not seen anything yet.