To the average user: literally nothing.

The downside of disabling it is the chance of bricking your expensive silicon, as the drivers to it are mysteriously inaccessible to the operating system, but I literally can’t think of anything else to add once it’s already down. It’s not-end user facing, there’s no API for it, it’s basically just there to be a firmware back door for the NSA and possibly extremely skilled foreign hackers. It doesn’t affect the actual processing layer of the chip at all IIRC.