We use DevExpress here in the IT Department to fill in some of the development gaps we have. We originally purchased it as an addendum to our ERP software that used the reporting package, but now we have used it to build several tools that the business has come to rely upon for business analysis.
DevExpress really is an expansion of DevExpress. I haven't tried too many other add-on tools to Visual Studio, but DevExpress is a valuable addition for us. We really like the dashboards and cards we can easily build within them, as well as the more powerful tools. As I stated earlier, we originally got a license because of the reporting package, but we tried the rest of the tools and found them just as valuable.
Great for analytical tools, can make pretty quick and powerful apps. Not as easy to use to make mobile applications, or applications that tie into existing databases. The latter is possible, but it is not as easy as creating a database from scratch. Also, their quick build tool is a little inflexible. Support is very good and quick to respond to queries.