One minor annoyance with JSON -> CBOR: If you feed it a value like 0.8, you'll end up with a 64-bit (8 byte) float. I'd love to see a type for simple engineering notation, eg: 8e-1 would encode the 8 and the -1 in as few bits as possible. I know there's a 16-bit version of IEEE 754 but the precision isn't there. Not sure how high the exponent would need to go to make it worthwhile.