dont worry about apostrophes, we can fix those later. so, when should you really start thinking about an API Gateway?

So, lots of us are looking at breaking down our big old systems into smaller microservices, right? And as we do that, this API Gateway idea keeps popping up. It makes sense, on paper anyway, for handling all the outside stuff like logins, checking how often people can hit our services, and that kind of thing. But I'm wondering when it actually makes a *real* difference for folks. Is it worth throwing in all that extra complexity right at the start, or should we just wait until things get really painful? What's your take on using API Gateways, and what were the biggest downsides you ran into?