I haven’t! It seems akin to ACP, is that accurate? Do you recommend it?
No, ECA doesn't work like ACP, it's provider-independent and operates similar to an lsp-server. It is in fact, written by the maintainer of lsp-mode and author of clojure-lsp.
I've tried many different tools for AI tasks in Emacs, eca and gptel remain the bread-and-butter of my workflows.