My daughter had a posterior TT and a lip tie that were both clipped at 2.5 weeks. The decision to do it was scary - I was afraid of having someone in my baby's mouth with scissors, and since it is not a well known problem, I was also afraid that the doctor I took her to would turn out to be a crackpot. (She wasn't! She was incredibly kind and smart!) But nursing was soooo incredibly excruciating, even with a shield, and she could not take a bottle, so I felt it was the right decision.
Also, I found out at the appointment that I have a tongue tie too, and she probably inherited it from me. When I was 18, I had to have jaw surgery to correct my bite (none of my teeth met except my back two molars - I couldn't chew) and the orthodontist who did my braces beforehand told me it was my tongue that had caused alot of the problems, and that unless I could retrain my tongue, some of my bite problems would return. I really tried to retrain my tongue but it was impossible. I did not understand what he could have meant until I started reading about DD's tongue tie, and now I know why it was impossible for me to do. So now I am even more interested in making sure her tongue works right because I don't want her to have to go through the years of jaw pain, bite problems, chewing and swallowing problems I have had, if a five minute procedure now can prevent it. I also have a high palate, and the doctor who did the TT clipping explained that a high palate is linked with recurrent ear infections, which I also had as a (breastfed) baby. I am even thinking of getting mine snipped now, to make swallowing easier, because I swallow a lot of air all the time.
Cutting the TT was bloody! I held her body while she was swaddled and a nurse held her head. The snip itself wasn't too bad - it was fast. She seemed pissed having people up in her business, but I started crying with her when the doctor had to hold the gauze in her mouth for four minutes.
I wasn't able to pick her up and comfort her. She screamed the whole four minutes, and it was probably the most awful four minutes of my life so far, but she calmed down immediately after the doctor took her fingers out. I got to hold her, and then nurse her pretty soon after. If your baby's TT is thinner, or anterior, there probably won't be much blood, and may be no need for gauze, etc, so it might not be too bad.
She did want to sleep right on my body for the next week or so, and my mom thinks it is probably because she needed to be comforted after the trauma.
She has more tongue mobility now, but breastfeeding is still not going well. We are working on it though. I was supposed to massage the bottom of her tongue to keep it from healing back together. This may not be an issue for you (if it's anterior), but it was really hard for me to do because it made her angry, so after a while I didn't really massage it, and just made sure I could see the scab to know it wasn't growing back together. I think this may be why she still can't extend her tongue far enough. If I'd massaged it as it was healing, it might have stretched out more. So keep that in mind if they tell you to massage it - really try and do it.
I found that the best way to do it was to hook my index finger over the lower lip, instead of trying to lift the tongue up or push it toward the roof of her mouth - unfortuately I discovered this after she was all healed.
So we are seeing a lactation consultant soon to see if she needs PT or if the snip has healed together more than it should have. I would also recommend trying to see an LC soon after the snip, to help with latch and things like that.
Well I hope some of that information was helpful for you. Good luck making your decision!