Our experience with RDX has been nothing short of spectacular. We currently use them for SQL support as well as PowerBI/Data Warehouse support and design. They are always there when you need them. After hours support is excellent as well. My account manager is simply amazing! Their expertise in the areas I hire them for is quite high. When we have an issue, they are right there to resolve it.
Nothing comes to mind, If anything, I would say their billing could use some modernization.
Check referances. These guys are honest!
I do not have to hire an in-house SQL DBA. Using RDX is much more efficient and cost effective.