iPad for sheet music display?

Is anybody here using an iPad for sheet music?

I've been hesitating to get an iPad until a model with a larger display comes out, since a 9.7" diagonal screen seems woefully small for displaying sheet music at a useful size (about the size of a trade paperback book). The MusicReader site lists other devices that can display sheet music, and most of them are larger than the iPad. HOWEVER, I don't want a Windows or Android tablet, and I don't want to spend a fortune on a device that is only for sheet music.

My plan is to scan my library of sheet music (hundreds of pages), which is mostly in the form of traditional music books now, including "real book" (lead sheets - melody + chord names) and regular treble/bass piano notation, sometimes with lyrics. Ideally, the software would enable transposing (as iReal Book does, for example). Very Nice To Haves would be the ability to annotate and highlight the notation, and hear a (probably cheesy General MIDI) rendition of what the tune is supposed to sound like.

Here's another article of interest (although it's a year and a half old at this point):
A Comparison of Five iPad Sheet Music Readers