My quick observations:
* It's nice to write TypeScript as the configuration language
* The provider documentation is poor and lacks the examples that terraform has, I find my self reading terraform documentation to understand how to configure Pulumi.
* You're constantly fighting with "async" vs "Input" vs "apply" when using a value, basic cases are handled in Pulumi but as soon as you want to do something complex you're toast. Maybe I just am doing it wrong, but that goes back to the lack of docs.
* How it handles dev/production/staging is just a little off from my expectations, not that terraform at it's core does this well either (why terragrunt exists).
Overall it's not bad, but it's not a silver bullet either to the typical problems. And suffers from a "small" community problem where you can't google solutions to problems with the same success.
My understanding is that this essentially uses TF as a backend