For the last few months, I have been using iGigbook on my iPad.
I loaded all of my pdf real books AND my original songs.
I use it for jazz trio gigs, praise team, and solo vocal/piano gigs.
Its $15.
iGigbook site


I also have iRealBook, which is very useful because it has changes for hundreds of songs (downloadable from their forums), but it does not have melodies or lyrics.

-rob