Tips on getting good results
Tips on getting good results

Getting great results may take some tweaking. The most common problem is that highlights in digital photos are usually clamped, and it's not possible to tell the difference in brightness between a white paper and the sun for example. The highlight boost feature takes the clamped values and amplifies them, as an attempt to extend the dynamic range. Sometimes this works quite well. Experiment with decreasing the amount, increasing the boost, and changing the falloff.

If you have photo in RAW format, it can make a big difference how you adjust the exposure compensation and recovery in Camera RAW or your RAW converter. Try to make sure that only those pixels get maximum values (100% / 255), that are really highlights - ie. where you would like the star effect. This might mean the image will be somewhat underexposed, but you can adjust the brightness or levels after you have applied the filter.

There are no such issues with HDR (high dynamic range) images. It's definitely worth taking a few shots with different exposure times, so you can merge them into an HDR image. You can find many tutorials on the web on how to do this. No extra software is needed, Photoshop can merge your shots. (File>Automate>Merge to HDR...)

The image also tends to lose contrast/sharpness when the filter is applied. Use Adjustments>Brightness/Contrast and Filters>Sharpen>Smart Sharpen to compensate for this.

How to color the stars

You can set the frequency of the rainbow effect low, this way you get colored stars or just a slight color spread in them. You can now use the hue offset to change this color. This can be useful for artistic purposes.