I've got one and don't notice too much of a difference with the dust factor honestly. But then again, my wife and I are good about keeping the apartment clean.
Where they really excel is when you have pets. They really do reduce the smell and allergens of them.
Ex. I had a friend whose apartment reeked of cats (he had two). Since I'm allergic I could only stay inside for about 10 minutes before I was miserable. The next time I came to visit he had gotten an Ionic Breeze and when I walked in I couldn't smell the cats at all. I was there for at least an hour with no ill effects. That's what sold me.
