>>>>"Yes with 1DS, you shoot 800 images, they are all on one folder."
That's good to know.
>>>So if don't shoot continuous , they everything would be in one folder? that could work for 10D in which shoots don't spill over to more than one card.
No, if you're asking me about the 10D, you'll still have the folders, 100 images max each, whether you shoot continuous or auto reset.
>>>What is the "downloader Pro" for Mac.? Right now I just drag and drop from card reader to folder on HD.
A nifty $30 utility by Chirs Breeze of Breezebrowser fame:
http://www.breezesys.com/Downloader/