I have a 7" tablet and have sort of used it with the piano. It's ok if I pretty much know the piece and want a crutch. I really can't see it well enough with or without glasses to use it well. I found that when I put the same file on a larger tablet in the store I could see it well.

With a computer you can convert scans or photo's of music to .pdf's, but I have found it's hard to find stuff once you get a lot of it.

Once scanned I'd use dropbox or something like that so that you can get ahold of your stuff from a distance.

John Conley
Musica est vita