I've got one as part of my security system and I love it.
The only con would be that it is heavy and a bit bulky to carry in your jacket when riding. It does, however, come with a nylon fabric case that can be strapped to the frame for travel.
The alarm is fantastic. If you fiddle with it even a little, it screams. It also serves to prevent the owner from driving off with it still attached.
I purchased all my security stuff from
BikeBone.com - great service and very reliable.
