I didn't go to Facial Team -- they weren't around when I got the full works done near the turn of the century.
Happy... isn't the right word. Letdown certainly isn't. These questions don't reflect the right paradigm for what it's like. My friend V calls it "the real sex-reassignment surgery." For the vast majority of us, there's some ambiguity in our presentations, at least at the facial level. That ambiguity goes away with FSRS. The "lag time" it took someone to read me and gender me female disappeared -- which for me was on the order of losing a second or less, but still, I could tell I was now being gendered female automatically, subconsciously, on the part of people meeting me. No makeup, barely any breasts, pretty tall, and still... suddenly people were clearer on who I was than I was.
For a good couple years afterwards, I kept expecting the bottom to fall out. It never did.
Now I'm not saying it's the end-all cure-all. You gotta have your facial hair gone. You've gotta have your voice down. You've gotta be reasonably competent doing female culture. But V is right -- it truly can be on the order of Sex Reassignment Surgery -- and yes, I'm using that term deliberately. It isn't a confirmation. It's about effecting an instant reassignment of who you are to the rest of the world. Not instant after surgery -- it takes a good couple months to heal up from this -- but instant on the part of people gendering you.
Happy... no. It's earth-shattering.