They've worked out great for me. I have quite a few indicators of various types to display telemetry in the UI to the user during a test. The shared variables are all written in a particular background thread. I don't use a "gazillion", though, perhaps no more than 40. I'm able to read, process and write the shared variables (and see indicator updates) at a 60 msec rate under Windows XP on a PXI controller.
