A while a go I wrote the inital script and post about it here. Due to my experience over the last few weeks and to meet additional requirements it was time to go over the script and extend its functionality. I thought about updating the previous post, but due to the major changes I decided to create this new post.
Update May 30, 2016:
The script will query multiple performance counters from Exchange servers in a given AD site.
Default counter collection
MSExchange RpcClientAccess\User Count
Shows the number of users connected to the service.
MSExchange RpcClientAccess\Connection Count
Shows the total number of client connections maintained.
RPC/HTTP Proxy\Current Number of Unique Users
Shows the number of unique users currently connected to a back-end server via RPC/HTTP.