I never used one, but installed one for a guy a while back. He used it for about a year before changing vehicles and then decided to change the siren. It's a good siren, especially if you're getting it for a decent deal. Covers your basic tones just fine and doesn't sound too "cheap" for being a slim, basic siren.
We go through tons of them and their cousin, the MS4000U. Literally by the pallet load quite often. They're great sirens and very reliable. I have absolutely no hesitation recommending them to anyone, especially for the price and the size of them. Their only downside is that they don't have PA, and are 100w only.