I am a songbook fan , sure... It is fast and stable on stage.
But be careful with this new syncing with dropbox! It takes much time because all your songs wil newly be indexed. With large number of songs , say 2000 you will need hours! . So put your iPad on external power, disable automatic shutoff , be shure to have strong and fast wifi and let sync run before you go to sleep! Next morning , hopefully, it wil be ready!
After initial syncing the next time syncing will be much faster... end good, all good. If interrupted, sync wil go on where it stopped, so you can split it.
But better dont start it just before a gig..
Nasty hickup, but inevitable, after new sync songbook works fine , as ever .