I would say it is if you are familiar with the situation. In order for something to have a chance to be a good date you have to be familiar with the situation you will be in and be able to be cool and confident.
If this isnt your first concert and you know the members of the band then I would say you are good to go. Me on the other hand, I have never been to a concert, it would be a bad choice for me to take a chick to a concert if I have never been to one.
Imagine renting a boat and taking a girl out on the lake for a date. That would be an awesome date that she should love. But what if you have never ran a boat before? You wouldnt be able to figure out how to get it started, fumble around with the ropes tied to the dock and then finally awkwardly steer yourself away from the shore. Thats not the kind of image you want to give and what could of been a great date became so-so.
I might of ran with that a bit too long.
Bottem line is its your call, if you are familiar with concerts then I would say it will be a good date idea.