The EOS 30 is superior technically to the D30. For example, the D30 is slower in terms of frames per second, and has only 3 autofocus points.
The D30 allows you to select an ISO rating of 100, 200, 400, 800 or 1600. The slower the setting, the higher quality the image. I shoot almost exclusively on ISO 200 (there's almost no discernible difference between 100 & 200), but increase the ISO where it becomes necessary to maintain a reasonable shutter speed, or when using a very long lens.
This pic has the ISO cranked up. I can't for the life of me remember whether I was using ISO 800 or 1600 though - but you can see the increased noise.
Click for large version
Photo © Chris Sheldon
As regards bracketing, the manual claims 3 shots per second in continuous drive mode. I think this is a little optimistic - more like 2.5 frames a sec, so it would take you just over 1 sec to take your auto bracketed set of 3.