My 20D, BG-E2 and extra BP511A arrived today, as promised by Park. 
I haven't had time to really play with the new camera yet, but I did try one thing; shooting burst mode (Large Fine JPEG) with a Sandisk Ultra 1GB CF card, the camera shot 31 photos at full speed! I guess that shows how fast it is writing to the memory card! 
The maximum number of shots possible in each burst depends (obviously) on the size of the written files. To prove this, I shot a full burst on manual focus with the lens cap on. The practically pure black images compress to very small files. It took an astounding ONE HUNDRED AND FIFTY ONE photos! at 5 fps! Although useless, it shows that the background writing really works!
RAW seems limited to 6 shots at full speed, whatever the shooting setup. 

