Pardon me for asking, but is there actually a version for the SD870IS (IXUS860)? The Wiki lists the camera under supported cameras on the main page, but
Index of /hdk/autobuild/ has a zip file that only contains DISKBOOT.BIN, no firmware file (that is why it is so small). I presume something is going wrong in compiling it, or it does not actually exist. The other recommended site does not have any version for these cameras. Is there a version that works? I had CHDK on my SD1000 and loved it, checked the wiki for support before buying my new 870, oops! Thanks!
Edit: Ah, I should have looked at the FAQ more closely, I see that this has to be placed on a bootable SD card, that is why there is only one file. I should be able to get it going then, sorry about that.