when should you think about using a service mesh

Hey everyone, I've noticed more chatter about service meshes, like Istio and Linkerd, recently, especially for handling microservices. They pack a bunch of features for observability, security, and traffic control right away. But, they also add a new layer of complexity. I'm really interested in what folks who've actually used or thought about using service meshes have to say. When did you decide it was time to add one? What issues were you hoping to fix, and did the service mesh actually help? Are there certain project sizes or setups where you think it's a no-brainer, or on the flip side, where it's just too much?