is the U2charist a good way to get young people to come to my church?

There is no one-time thing that a congregation can do that will attract and retain people who aren't attracted to what goes on in the congregation the rest of the time. People can (and do) sing along to U2 CDs and DVDs at home, and if they want to hear and sing along with a U2 cover band, they can do that in bars and clubs. That's not what the U2charist is about at its core, and I don't think that's what attracts most people to a U2charist.

The U2charist is a demonstration of one way that liturgy can bring people together to celebrate what God is doing in the world to bring justice for the poor and reconciliation for the world. It is by no means the only way to do so, or even necessarily the best way for your congregation. If your congregation doesn't really know or like U2, it may feel forced and awkward to use their music without substantial adaptation in liturgy -- and if it feels forced and awkward for you, that's probably going to come across to anyone who does visit your church for the first time for a U2charist. That probably wouldn't be the best sort of circumstances in which to try such a service; there's little that's cool or fun about a bunch of people doing something that they think is no fun at all because they think it would look cool to others. On the other hand, if a U2charist does sound like a fun and exciting thing to do, that will probably come across during the service, and I say go for it! Those in your congregation who choose to participate will enjoy and be energized by it even if the service doesn't attract newcomers.

So no, I don't think that announcing that you're using U2's music for one service is going to result in unchurched people beating down the church doors. That doesn't mean that a U2charist can't play a role in actively inviting people who might choose to join your congregation, and here's the role I see it most often playing in a positive sense:

If your congregation is actively and consistently engaged with and excited about God's mission in the world, and if a U2charist is for your congregation a natural expression of that, then your hosting a U2charist can provide an opportunity to let people in the larger community know what kind of a community your congregation is. I don't think it's U2 as such that attracts people to a U2charist. I think it's that many people want to be part of a community that believes that the universe arcs toward justice because it was made and is loved by a God of justice, and that is excited about being a part of this movement of God's Spirit in the world. I got the idea for the U2charist in the first place because that's part of what a U2 concert feels like for me, and I think there are lots of people who feel similarly -- who like U2, and who associate U2's music with a sense of connection to something larger and exciting that is going on spiritually in the world.

So the short answer I'd give to the question is this: People will join your congregation when they sense that your congregation is a community that's a part of and that supports its members in engaging the exciting work of God's mission in the world. If your congregation experiences that in U2's music, then a U2charist could be a helpful way to grow that sense within the congregation until there's a critical mass of folks who feel that way who can welcome and support newcomers who arrive hoping to find that. If your congregation already has that critical mass, then a U2charist might, with good public relations around it, help get the word out in the larger community that this is what you're about. And whatever you do with respect to having or not having a U2charist, a focus on God's mission of justice for the poor and intentional work to celebrate that in liturgy should be a consistent emphasis, not a one-time or very occasional add-on, whatever music you use in worship.