The scalability is quite good. Every new upgrade comes with new features, so it's quite a versatile solution. 

Currently, I have 80 users for on-premises, and 20 users on the cloud. Whenever we have a renewal on the licenses we keep on adding more users. Right now our numbers are increasing.

I don't think scalability really comes into play because it is an anti-virus solution, so one expects it to be on all the endpoint. 

We have 2000 users on the solution currently, but we do not plan to increase usage. We're in the process now of switching to a different solution, so we don't plan on testing the scalability of it.