I was going to post this on a different thread, but here's the perfect opportunity. I got an iPad 3rd gen with retinal display just after Christmas, then DLed the app forScore which lets you import music PDFs. I now have all 3 vol of Real Book(something like 1,200 pages), whatever music the bands at school are working on and even a full musical(which I will delete once the performances are complete). And oh yes, the entire Arban's(of which I own the original) and most of my private lessons warm-ups and drills. Regardless of when I use actual sheet music, I take my iPad now as back up. Even though the screen is slightly smaller than standard paper, the retinal display is such a high resolution, it is easy to read.
forScore let's you notate right on the PDFs with your finger or a stylus AND tie mp3s of music TO the PDF music, I have several of my most played jazz standards linked so you can actually play the music file from the PDF music.
The technology is simply amazing and I think will change the way we do things in the coming years. There are foot pedals available now so you can turn pages and not stop playing. There will always be a place for sheet music (just as the whole book to ereader debate), but used as an effective tool, tablets and appropriate apps are really quite incredible.