I ordered this filter for my Nikon D90 using a Sigma 18 to 200 lens and, to be honest, did not expect much at £3.24. I went ahead with the purchase as I thought at the very least it would protect the lens in wild situations. The item arrived the day after in excellent condition and I immediately thought I would give it a test.
It fitted well and does give a good star pattern when photographing bright lights, from memory the star flare was maybe slightly more hazy than my 52mm Hoya but it's hard to tell as I did not compare images directly.
I also took two images in a bright room, one with the filter and one without, just to ensure the sharpness of a standard image was not affected. Honestly I could not tell the difference between the two pictures when viewed side by side on my PC monitor with full zoom.
I am slightly disappointed as I could not rotate the pattern independently but this is not a big issue. I don't know how long it will last but the quality appears to be good and at such a low price I have no complaints. If you want that starry night effect this is definitely worth a try.