I can vouch for Haystack and I'm very happy to see this news. I have started using it to build my company internal RAG platform. It feels way more confortable than using other LLM orchestration looks like LangChain or LllamaIndex, they always felt way too bleeding edge for me with too many breaking changes.
Reading and working with Haystack code was a pleasure and I could even contribute a few time to solve some of my issues or missing features ! A very good foundation for building LLM app. Also it's backed by a company called DeepSet and Haystack exists for multiple years so I guess it's here to stay :)