Interesting discussion just came up on LinkedIn, which I think highlights both the biggest opportunity and the biggest challenge for Pulumi. Someone was complaining about how their 2000-resource Terraform workspace took 10+ minutes to plan. I asked if they'd looked at Pulumi. They hadn't, and were delighted to hear about it, but they said they didn't want to add another tool to their stack. (I sympathise with this; I think everybody feels like their stack is already overweight. The barrier to entry for a new thing is high.)
How does Pulumi perform relative to Terraform for very large workspaces?