In my case the interactive performance when using "ondemand" is highly noticeable when gaming or while using some apps like Firefox. It seems to be a known problem [1] with GPU intensive tasks.
The problem is switching not occurring, or occurring too late - with the OS shuffling a single threaded app around I/O units it looks like the CPU usage is say 20% so no need to move to higher clock.
The I/O and Ram paging situation far dominates.