This product is quite reputable in the delphi world and they are a late comer to the .NET world.
My main reason for using them over the others are:
1- right-to-left support. While .NET natively supports RTL for Arabic and Hebrow, many vendors (specially DevExpress) choose that its not economic for them to add such support
2- maturity. Some of the market controls are not as mature and you experience that the once you start creating some advanced reports
3- Client Side. Fast-Report is designed for client side reporting and this is not a second thought for the product (as in SQL reporting services)
4- speed. Fast-Report is really fast compared to the rest. I have compared it to CR and Telerik
5- Easy. Coming from Access this is the only tool that could come close to the easiness of access in creating reports
6- price (ActiveReports is way overpriced)