Curiosity only. Is there anything I can do with a 128GB WiFi iPad Retina that I can't do on my 2012 27" iMac? I'd love to have one for email, browsing, music, video etc. wandering around, but other than portability, I don't know enough about it to understand justification for buying one. I need my iMac for complex Excel and Photoshop stuff but it might be nice to add an iPad if it had some unique virtue other than the camera in the back.