I've done it but not tried it in anger since.
Angie's having the E-P1 this weekend for driver hunting and it won't be used for sports.
So I won't be able to report until next week.

Managed to get one or two race photos sharp last weekend, before the update

C-AF seems the best way to get focus on a car, but it still doesn't pan for me
I have C-AF set fo AF priority, not release priority, so it won't shoot unless it thinks it's in focus. That could be 3 or 4 seconds after I start panning, so I don't get the shot I want.
But my eyesight even with glasses means I can't get critical focus using the screen. It's just too close to my face.