Implemented Istio? Could you explain the challenges you faced?

Used it in Kubernetes. When there's a breaking API change, imagine how terrifying it is and has been to try to upgrade everything in the Istio control plane when possibly your entire cluster's communication, observability, security, etc are all going through the same system. It became less stressful to do all the planning to build a second Kubernetes cluster and switch over with the new version already installed.