I have had the factory OEM alarm system on my hatchback MINI (2002) for 2 years now and at first had sensitivity problems with intrusions such as hands, leaves, etc...through open windows, UNTIL I learned of the second setting - alarm on, but desinsitized....by simply pushing the lock buttom twice, quickly, when locking. Then there are NO PROBLEMS ! ...... Never had any kind of problem with rain. I think it is a very good alarm system. I would certainly buy it on another MINI ! 
