The biggest cost comes from managing another namespace with a handful of deployments and pods. There's also all the sidecar containers that are taking up resources, even though not very many. This literally costs more, but maintenance has been minimal. The pros outweighed the cons significantly and we saw faster responses and lower latency due to the intelligent load balancing. Our pods were being loaded unevenly so when Istio balanced this out our scaling worked better and led to much faster response times across the board. So far we have not run into any new failure modes or other issues. Istio has been "set it and forget it" so far since we are using a pretty vanilla installation. Thank you for the great question and I hope this provided some insight!