I have "The New iPad", AKA "iPad 3". I use it to review photos after a shoot. I've been meaning to write a blog post about my workflow, but haven't yet gotten around to it. Suffice to say that at the end of the day, I use Apple's Camera Connection Kit to copy photos directly from my camera (currently a Nikon D800) to my iPad, where I can quickly and easily review the photos on the high-resolution display, and see what I've got. I can then delete the ones I don't want to keep, and I import the 'keepers' into Lightroom, directly from the iPad.
With the introduction of iOS 6, the iPad would no longer import photos from the Nikon D800. There was no useful error message - Just a red exclamation mark over the thumbnail image, rather than the nice green tick displayed when it's been imported successfully. This is something that worked fine in iOS 5, but suddenly no longer worked after the upgrade to iOS 6. Other cameras which also apparently fail are the Nikon D600, and D3200 - All high-resolution (MP) sensors.
After a lot of Googling, I found several forums suggesting various 'fixes' that didn't work:
All I had to do was close down the apps I had running. You do this by double-clicking the Home button, and closing down the icons along the bottom of the screen. I restarted the iPad, but I don't think that was really essential. Now the iPad is back to importing high-res RAW files from the D800. I guess the cause was either that the Photos app needed closing and reopening after the iOS 6 update, or that I simply had too many apps open at once, and the iPad didn't have enough RAM available to process the large photos I was trying to import.
Hey presto. Hope it works for you.