I had a customer many years ago that used RMS. They used to have an integration to Sage100 (MAS90 back then). It wasn't a tight or real-time integration but basic ""end of day"" updates of Inventory and AR. If I recall correctly, they always seemed to have issues with both the RMS software as well as the integration part. Upgrades were not easy. Customer was bought out and switched to another package. Keep in mind that this was over 10 years ago, so things might be different now..