If you want it because YOU like it, then go for it, but don't do it to please other people. I had my tounge pierced when I was 17, 12 years ago as I am now 29. I had it up until about 3 months ago, and I never had any problems with it. I only took it out because of...well....let's just call it an "oral sex disaster".....lets just say, barbell balls and urethra's don't fair well when one accidently sticks in the other! Anyways, I took it out so my boyfriend wouldn't fear that happening again, hehe. Oh, it really doesn't hurt much at all, out of all my piercings, ears included, my tongue was probably the least painful one. If you do decide to go for it, make sure you go to a reputable piercing shop. A piercer who doesn't know what they are doing CAN cause damage, especially with the tongue.
Be aware also of the possibility of infection. Tongue piercing is about the worst from that angle because infection is not always visible at the site of the piercing. There are countless germs in the mouth, so it is impossible to keep the site clean. So bacteria can seep into your blood stream and start an infection just about anywhere in your body. In one case I know about, a young woman developed an infection in her brain. She had not been feeling well, but by the time they identified the problem, treatment was too late. Be careful.
I got my tongue pierced in June of 2003 after a long time of waiting. It was a brief sting that was followed by some pain but its bearable, but obviously everyones pain tolerance is different. My tongue was swollen for about 3 days. Really it is nothing to stress about because I know I was stressing for nothing. Well if you have any more questions, I will be glad to help.
Investigate your piercer! Investigate your piercing shop! DO NOT LET THEM USE A PIERCING GUN!!!
Piercing guns shouldn't be used on anything, even ears. (What? Then what are they for?) They're a worthless invention, because they can't be properly sterilized in an autoclave. ANY piercer worth ANYTHING uses a needle not a gun. Any shop that doens't have an autoclave is shady and should be avoided.
BTW saliva is sterile and helps keep the piercing clean. Just have to be careful. Tongue piercings take a long time to heal because of the high activity of them.
G'luck with it.