Perhaps some additional feedback on this topic. I've been playing with the camera connection kit, and have found it is pretty easy to import files onto the iPad including most raw files. To get them off the iPad, Lightroom 3 beta 2 sees the iPad as an external device much like a card and you can copy the files onto a location of your choice on your hard drive when you import them.
Using a cheap belkin card reader I had no problems importing from several CF cards. The iPad supports most raw formats, and you can view the raw files on the device. I found that even though it doesn't support PhaseOne files, as long as i have my phase one back use the .TIF extension instead of the .IIQ extension, I can import the raw files from my p65 onto the ipad and then back off to my hard drive using Lightroom. I can't view the phase files on the ipad, but could use it to back the files up.
I had no problems keeping the original file names for any of these steps.
One thing you can't do is write the files from the pad to another backup device such as a small USB hard drive or another SD or CF card which is the way I typically like to work during a trip (3 copies of each file, one on the original card, one on the laptop and one on an external drive).
The other issue is you can't really organize the files on the iPad. However, when importing them in Lightroom you can set it to separate the files according to date.
I'm going to load up a set of cards from a recent trip, simulating what I would have done when in the field to see how functional it might be to use the iPad as a field backup/secondary storage device.