I haven't done as much as I would like with them, but I feel like until someone tries type providers they don't get just how powerful they are. Being able to point to an example .csv file and have it generate the classes for you, and update them if you change said format, in a way that it ensures the types still work, is amazing. And you can do it for ANYTHING as long as you have a way to extract the data to feed it to the compiler.
I still need to learn how to write a type provider just so I can.
I still need to learn how to write a type provider just so I can.