I worked at a place using pg_queue (the person who created it worked there before going to Skype IIRC) and maybe it was working well operationally but it was not a great experience to develop on it. It was hard to generate events and debug/observe them (it was height years ago so the details are a bit fuzzy).

MS also moved from it afterwards when they acquired Skype but I guess it was more because of the shift to SQL Server.