The one thing metric screws up is file size.

A gigabyte is 1000 megabytes or 1,000,000 kilobytes or 1,000,000,000 bytes.

A gibibyte is 1024 mebibyte or 1,048,576 kibibyte or 1,073,741,824 bytes, because it needs to go by increments of a power of 2.

This would be fine except gigabyte also means gibibyte. So if a file claims to be N GBs, I don't know if it actually means metric GBs or GiBs.