I think changing the mouse pointer on "busy" or "working in background" is OS (whatever it is) only territory. Showing rotating sand clock cursor on any web application will give the visitor wrong impression of overall system instability. So I think you have to leave cursor changing as an option.
It is better to show loading/busy animation only if it is necessary – when loading or processing actions distract user interaction with the application.
Case 1 - Application Load
If the application is usable at this time, no indication is needed.
Case 2 - Page refresh
It is better to show the indication over the individual panels which are refreshing.
Case 3 - Modal Dialog / Wizard
There are enough indications here that something is going on. No need for changing the cursor.
Case 4 - Load-On-Demand
It’s OK so.
the Telerik team