I just tried several methods of transferring photos from my Canon 7D to my iPad 2 using the Camera Connection Kit. I was shooting both RAW and JPG, and used a Sandisk 16GB CF Card in my camera to save the photos.
Obviously, since the 7D takes CF cards and not SD cards, I used the USB dongle in the CCK. First I tried connecting the iPad to a Lexar CF card reader. I immediately got a message saying that the device requires too much power, even before I inserted the CF card into the reader. So that method didn’t work.
Next, with a CF card in the camera, I tried connecting the camera directly to the iPad using a USB cable. This method was successful. Upon turning on the camera, the photo program on the iPad activated and asked if I wanted to import my photos. I said yes, and all the images (both RAW and JPG) were transferred and viewable in the iPad.
Next, I tried transferring the 7D photos I just imported from my iPad over to my iMac for further editing in Aperture. This was also successful. My setup is such that when I connect my iPad to my iMac, the iMac’s Image Capture program is automatically started and from there I can move the iPad photos to Aperture or a folder. For these tests, I imported the photos into a folder on my desktop. I started Aperture (v. 3.1.3) and imported the photos in the folder into a new project. All the photos (both RAW and JPG) were successfully imported, including all the metadata from the camera. From there I could manipulate the photos just like any others in Aperture.
During my tests, I found that the choice of USB cable you use matters. At first, I used a thin USB cable that I had previously used for charging duty (in fact, it has a label that says Charging Use Only on it). It didn’t work at all for transferring data. However, when I switched to a thicker USB cable (from Apple coincidentally) that could handle data, the photos transferred from the camera just fine.
I still don’t think the iPad is the ideal photo backup device, due primarily to its relatively small storage capacity (especially if you shoot RAW), but at least these tests show it can in principle be done with higher-end SLR cameras that take CF cards.
Hope this helps someone.