Oh, nice find. Indeed, on a570is too the digital teleconverter speeds things up. When Tv or NR from high ISO doesn't slow shooting down, I get 2.0 fps at 1,9x digizoom (equals to 1600 pix width source image as seen from property #92) and 1600x1200 output jpg.
640x480 seems work at the same or almost the same speed even though the camera has to scale down the image(?). Scaling up to 2048x1536 slows it down significantly.
Digital tele 1,5x gives 2048 pixels wide source image, shooting to 2048x1536 from it gives a burst rate of 1.9 fps.
Shooting to 1600x1200 is slower, about 1.8 fps. This must be due to scaling... scaling the smaller 1600x1200 to 640x480 is so much faster that I couldn't measure it on this quick test.
Without digital tele I got 1.6 fps at full 3072x2304 resolution and 1,55 fps at 1600x1200.
I shot superfine quality to a Sandisk Ultra II 1G card, no RAW obviously, in M mode at Tv=1/1000s and ISO80.
(I measured the time it took for 50 shots for these figures, not very accurately)
