No trailing commas and multi-line strings are my other two big complaints. The ability to leave keys unquoted if they don't have any spaces would also be nice.

No trailing commas and multi-line strings are my other two big complaints. The ability to leave keys unquoted if they don't have any spaces would also be nice. The best part is that these are a superset of JSON and could easily be added if there would just be more buy-in (lots of unofficial support already exists).