Kubernetes Pod Autoscaling in practice

I am curious to hear people's/companies' experiences using Kubernetes Pod Autoscaling (primarily thinking of Horizontal Pod Autoscaling, but also interested to hear if/how people use Vertical Pod Autoscaling).

When I Google around, I find lots of blog posts of the form "here is how to set up k8s autoscaling based on CPU utilization/custom metrics..." but I don't find much of the form "here is my/my company's experience actually deploying k8s autoscaling in the real world..."

What metrics do you use to autoscale? How do you select/set the autoscaling parameters for your real-world deployments? Are you happy with the experience? Are there any pathological cases/issues you frequently run into?