LinkeSoft SongBook

The most compatible music reader app - as long as you only need ChordPro.

unrealBook

You just gotta love an application with a transmogrify button.

MobileSheets (Pro)

Odd user interface and odd update policy -- too bad for an otherwise good app.

Fakebook Pro

The Fakebook Pro is my app. Featuring the functions I need. Working in the way I want. Perfect for my gigs. That's it! But judging from the popularity of the app, the Fakebook Pro might be right for you as well.

GigBook

A good PDF reader app with some really nice extras for musicians. Unfortunately the latest versions seems to have stability issues.