@matigo My last iPad was the iPad 2, and its resolution is simply too low to read anything comfortably on — least of all scans of older publications.
I bought the 11". Was very, very tempted by the 12.9" for reading comfort — and just more if that beautiful screen in general — but figured it'd be so bulky that I'd never take it out of the house, which would be a real shame. It'd be too hard to hold in my hands on the train or bus, for example.
My other main application for the iPad is reading books. The Kindle (hardware) is great but the slow processor and screen refresh make it intolerable for foreign-language books where I'm consulting the dictionary all the time.