The stability of the solution is very good. 

They only time that we had issues with Stability was back when it was 11.1.1, since going to 11.1.2 the stability has been outstanding.

DRM is one of the most stable metadata applications if, as with any other tool, you use it correctly. Don't hard-code values into the properties as this is the largest culprit of customers saying that DRM is "running slow."

Another stability issue is what we call "cliff hierarchies" where you have a parent node and an excessive number of children. Once you get to a number of children that doesn't fit on a screen, maybe it's time to add another parent to break up that section of the hierarchy.

No.