The comments to that posting make it clear it is not the TLD per se, but the company that manages it. So *.co is as reliable as *.com as long as equally good companies manage them.
The risk is not that big. Even the described horror-horror was only a partial outage. Once a browser resolves the IP via one of healthy DNS servers, it caches it, and the problem is resolved for that user for an hour or so.
For APIs, especially where you provide your own JS (or any other) library it is easy to add a fallback to a secondary domain under another TLD.