It's actually low in price for a mic....think of the standard SM58, those are $100 and you usually have a more than one on stage.

I've never used that mic but it looks kickass and I did know a singer back in highschool who used an old school mic live on stage for vocals.

The spec sheet looks like it's a bright dynamic mic which doesn't pick up anything below 50dB so you won't get that really low end out of it. I would say let him try it and if the sound isnt what you guys are looking for, try the standard SM58 which picks up more range.
I think it is perfect for vocal use. As you know when people are talking the sound level is around 70dB i think, so when singing it is supposed that the leavel will be a bit higher. Overall it look bad ass and if your singer likes it so why not use it