I've been reading about it for years and it's always sounded very impressive to me - the magic sauce that you can sprinkle on regular PostgreSQL to have it scale horizontally - but I haven't yet had the opportunity to try it.
Citus uses physical replication for worker and coordinator nodes, and things start getting complicated when you're trying to monitor the status of all the replicas. With vanilla PostgreSQL, you don't have this issue. I'm guessing that they solve this in Azure with block-device primitives at the storage level or something along those lines? It's probably not insurmountable to do it yourself, but we're not yet at the grip-n-rip enterprise offering.
For my understanding about the multi-region DR capability you would want: Do you want to be able to write to the DR region all the time? Or do you want to be able to switch over to the DR region in case the main DC is down?
+ Implementation of the UK Coronavirus Dashboard running on Citus and Postgres, a post co-authored by the technical lead of the dashboard, Pouria Hadjibagheri: https://www.citusdata.com/blog/2021/12/11/uk-covid-19-dashbo...
+ Architecting petabyte scale analytics using Postgres and Citus, based on an interview with the user, Min Wei: https://www.citusdata.com/blog/2019/12/07/petabyte-scale-ana...
+ Video of a customer talk about scaling a SaaS application on Citus by Jonathan Denney at ConvertFlow: https://youtu.be/PzGNpaGeHE4