I think a little cautionary note should be added here. Flash and Media cards are not like conventional drive media. Some are not especially fond of having a file dragged off to the Macintosh trash can.
The safest and best place to store digital photographs and prevent a variety of potential problems is to copy them all to the Mac harddrive, "eject" the card from the USB reader, insert it back in the camera and use the camera's erase or format function.
I've seen several flash cards ruined. They would accept no more files (could not take photos), could not be erased or formatted by any means, etc. I'm -told-, but don't know, that this is a quirk of some brands, some models, etc. of cameras or the same qualifications apply to different brands of media.
I, for example, have used a variety of Nikon digitals, presently a Coolpix 880 and recently added a new D100 (6.1 Megapixels) for which I have a 1GB IBM minidrive (or whatever they're called). I've been told by experienced photographers to always erase graphics files via the camera's format command (the 880 also does crude QT), but that the IBM drives are "safer" to use in deleting individual files.
The idea of "safer" is one I don't find all that appealing. The driver for the media has a number of jobs to do. Then there's the question of the technology of the media. What if I go through and pick 87 of 144 photos to erase via deleting them on the desktop when the USB card reader has them mounted? That's a bit of a load.
Most cameras have the ability to individual "trash" files themselves, but they're using the technology designed by the vendor, not one that (hopefully) works from another party or which they've adapted to a third party's software.
I can sympathize with battery problems, but I look for that going in to the purchase when it can be avoided by only buying a camera that has the rechargeable feature that comes with it or is optional. And storing all photos via even a finder copy with USB is not all that onerous. I in fact often just create a folder on the desktop or in the /home directory, select all, and drag all files to the folder.
This whole issue obviously makes me a bit nervous. I think some generalizations have the potential for creating, not solving, a problem. 2 cents.
(or maybe 3 cents in view of the length :))