No some have had good luck using them. It just overloaded my scanners. I ended up selling mine.....Hoser
If you're in a metro area, with lots of signal sources, especially cell sites, the pre-amp may overload your scanner, giving you less reception. This is especially true if you connect it to an outside antenna in a large city. Depending on your location, the type of whip (rubber duck or similar) antenna used, in some cases, you may see some improvement, even in the city, but only if you are not real close to multiple sources of other signals (cell towers, broadcast towers, repeater sites, etc). That's been my experience.
I do use my GRE amp when I am out in a rural area, and it does work well there. I also used it when I had my travel trailer at some property we leased about 100 miles west of here. With an antenna on the roof of the trailer, and using the pre-amp, I could hear Dallas PD/FD quite often, as well as other signals from quite a long distance. Besides the lack of interference, we were on higher ground compared to the DFW area.