You know, Helen, I only got the ipad reluctantly, for a non-music purpose, but I can’t believe how great it is on a gig. With one of the apps for musicians (I use forScore, but there are others) you can not only replace big bag-o-tunes, but they have features like letting you set up “hot spots”, which are links within a piece, so that when you reach a da Capo or To Coda, you just tap and the music jumps to the spot you want.
Downsides: can’t see in bright sunlight, so it fails where it would be most useful, pages are a little smaller than on paper, and it’s a nuisance to get music into it, but when it’s suitable, it’s just great.
And then of course you have your tuner, your standlight, and so on with you, too, without bringing more stuff. With Square you can even swipe a credit card from a spacey bride who forgets the check.