dd2 had her tongue tie snipped a couple of months ago, she was just over 1 then. DH took her to see consultant and he just snipped it there and then. She was in no more pain than when she's had her injections and next day she began to babble for the first time in her life.
If I had known when she was newborn that she had tongue tie I would have wanted it snipped. It wasn't painful for me, but she wasn't thriving and it was very difficult for me to build up a good supply.