We had some AWS experience from running our backing services (RDS, Elasticsearch, Memcached, Redis) on AWS despite doing compute on Heroku for a long time, but we'd never done EC2 or EKS for deployments on AWS. Despite having been on Porter now for months, I'd say we still don't know or really need to know a ton about k8s, but we are familiar with some basics around pod sizing, healthchecks, deployments, etc.
I think Porter does a lot to put themselves out as as destination for people leaving Heroku. I'm not sure if this would have been more work to do something like Render, but I was very pleased with the timeframe, hours spent, and the ease of cutting over.
We have a monolith that handles ~50k/min traffic at peak use as well as a couple very tiny services that do some accessory stuff. All the apps are Rails apps.
One of the reasons that we chose Porter over other options is that we really liked their setup for Preview Environments, which are an important part of our workflow here. The experience of running preview apps on Porter is notably better than on Heroku, where we started to see a lot of unreliable behavior on app launch that resulted in the app being unusable and the only fix was to close and open a new PR .
On the whole this was a really positive experience for us. We're seeing better performance, we're paying less (in Porter + AWS compute combined) than we did for Heroku Enterprise, and our ability to deploy mid-day when we're under load is better than it was before. I've spent most of my 12 years or so of Rails development working on Heroku (and we had been on Heroku for almost six years), so we had some fear around moving to unfamiliar tooling, but this has been a big win for us.