I understand people can make errors when generating gerbers but they can also make tons of errors when sending you the kicad files (like not including custom libraries).
Creating Gerber files is sometimes hard as different fabs require different Gerber files. Starting with the file extension ending with floating point precision.
One argument against uploading KiCad files is copyright as the fab could reverse engineer the PCB. But this does not count for open source projects and is really unlikely to happen.
I'm thinking about flashing microcontrollers, soldering components, inserting PCBs I to cases, putting them into packaging?
Obviously the holy grail would be for them to do everything in small batch runs and handle shipping for you too, but I'm also interested in services which may do only parts of this.
Their end-to-end webapp is phenomenal and a great break when you finish a design for a client and the premium is just worth getting off your back.