I don't want to start a debate about a specific vendor but the cost was very high. Leaky serialization of call arguments and results, then hairpinning messages across the internet and back to get to workers. 200ms overhead for a no-op call. There was some observability benefit but it didn't allow for debugger access and had its own special way of packaging code so net add of complexity there too. That's not getting into the induced complexity caused by adding a bunch of RPC boundaries to fit their execution model. All that and using the thing effectively still requires understanding their runtime model. I understand the motivation, but not the technical approach.