So, when should you actually start using a service mesh?

Hey everyone, I'm trying to scale up our microservices and honestly, managing how they talk to each other is getting tricky. Dealing with stuff like retries, circuit breaking, and mTLS consistently across all our services is becoming a real headache. I've been checking out service meshes, you know, like Istio and Linkerd. When did you guys decide that a service mesh was the way to go? What specific issues did it fix for you, and what downsides did you run into? I'd love to hear what you've all experienced.