Best voices I know of
When I switched from iPod touch to iPad this app automatically updated itself to the proper version. However, it had an issue with redrawing properly when I switched from landscape to portrait orientation. That issue has been fixed, although the options buttons are not available in landscape mode. I love this app, because the voices are so much better than those built-in to iOS 7. I especially like Ryan, the male American English Voice. No other voice I have found is as good. In addition, this app can continue to read after you put your device into sleep mode, saving battery life. That in itself, makes this app worth the download!
Cybernettr about
Speak it! Text to Speech, v2.6