John, I had the same problem, with raw and dropbox, I think though that with photoforge2 you can process raw, but you have to import them directly from iTunes via the document sharing thingy!
You can import raw onto the ipad2 (or the original) straight from the camera using the connector kit...or, if you loaded them straight onto an SD card and then used the connector kit, that should work too. But, the iPad actually generates a jpeg from the raw file, and it's that jpeg any apps would use.
Also, when you import photos from dropbox on the iPad, it never saves the photo in the same resolution, always a lower one! (the developers say it's to save 3G bandwidth) but there's no option to change the quality on imports, only uploads. It's really annoying actually!