I use these for DH,they are excellent!.They are very comfortable and very grippy as well.
You have to make sure your feet are set in the corrected postion before leaving the start of the track because you can't slide your feet about,you have to lift them of the pedals to allow you to move your feet postion.
hehe
As I was on SPD's I had this issue for a couple of rides

But hey, my style and technique have improved sensationally since changing to flats!
But I still have to laugh as my friend just went from SPD's to flats and 5.10's.
On the first ride he complained the whole uphill that he can't move his feet
