We've owned a Bugasalt for two years. It works fairly well if you use coarse salt like sea salt (not rock salt). It will work on flies with table salt, but larger insects or those with harder bodies are just stunned. The larger, heavier, coarse salt grains carry quite a punch out to about 5-feet.
We give it to my grandson who goes around the yard "hunting" bugs with it. He's killed flying wasps with it - sort of like sporting clays, only it's sporting bugs.
If you use it indoors - it's pretty messy - you're shooting salt all over the place.