China has used it to disperse air pollution. Kansas uses it to reduce damage from hailstorms (to disperse the hail before stones get too big). And there are many experiments going on about how it can do exactly what you're saying: Mainly to redirect and/or lessen the might of hurricanes/cyclones/typhoons. Here's a Wikipedia article on one of those experiments: Operation Stormfury.
One thing to note is that air pressure is a major factor in creating such storms, and cloud seeding does not affect that, so its beneficence is questionable. However, there are politics going on too. With the increase in the intensity of cyclones being attributed to climate change, anti-climate-change governments are limiting the money available for such experiments.