I just repeated the process of swapping to the onboard graphics. This time I thought I'd hit the jackpot. CPU usage went down to low 50% range when I activated Hardware accel and restarted. Then I discovered that all of my motion masks and setting had dissapeared. So I imported my latest settings (which I backup every time I make a change), and all of the masks, settings etc were restored just fine. But, CPU usage went back up to the 90s (low 90s with hardware accell on, 100% with it off).
I'm just wondering if any of you are seeing these improvements in CPU usage at the expense of having lost any settings you had previously?