This App does what you need it to do: display lyrics while you perform, and enable multiple users to add or edit lyrics for everyone in the group. Having now spent many, many hours putting our bands lyrics into this App, and having used it in a gig, you will find that this is a very powerful and enabling App. Definitely buy it.
But lets remember, as a user group, that we can help to make it even better. Any software drives culture - the way we approach life and challenges; I have found that the lyrics from Chordie and other sites often differ from each other, or the way youve always sung it, and the guy who has the iPad now might think he controls the lyrics, and others may not be comfortable with that. So, my advice is to make this a collaborative venture, for sure, not just within your band, but together as a Songbook group. Does the Songbook site have a users forum? That would be helpful.
Be careful with Dropbox, you can lose everything if you synch when the file has been emptied. The are no warning windows in the Songbook App, and one would be helpful to prevent disabling disasters, for example "synching now will cause the loss of material - go ahead?"
Overall, a great App, one Ill be using for years to come.