Clear nc for this 
TL;DR - it's incredible, but be careful how you take it.
Full version:
Bliss. Absolute bliss.
The come up is weird. I don't like it but some people do. It's like hanging over the top of a rollercoaster. The adrenaline is there, I feel a bit jittery, which isn't always nice, and depending on dose and your surroundings you can feel a bit sick. I don't take pills so I have better control of my dose and know how to mitigate the other issues so it doesn't bother me as much anymore. Half of the side effects are because people are taking WAY too much. The average woman doesn't need a full pill at the strength they are nowadays. When I've had a higher dose I've found myself throwing up and feeling awful on the way up, and the actual high isn't any better.
When you actually come up though it's just incredible. You feel music in a way you never have. You don't just hear it, it touches you more deeply than anything you've ever heard. More so if you're already a music lover, and you desperately want to dance and express yourself without a care of what you like like. You also want to be close to people. Talking about things you would never normally dare talk about (it's a great way to have serious conversations you'd otherwise find difficult), genuinely wanting to listen, speaking to strangers and bonding (not at all in a drunks in a toilet way either) the sensation of touch is mind blowing, lights are brighter and everything is more beautiful. I've met people drunk on nights out and never stayed in touch. I've met people while rolling and we are still friends now even though we haven't taken anything together since. There's a reason it has been used in therapy to help people overcome PTSD.
I've only had one come down out of my maybe 10 or so experiences.
I generally take with dp and a small group of friends, with new people joining or people missing a session as they want to. We're as careful as we can be. We buy mdma in crystal form rather than pills, we test it with a testing kit, weigh with very sensitive scales, we have worked out the lowest dose to get the wonderful feeling without being silly about it. We take magnesium to help with the grinding and 5HTP afterward to help with serotonin depletion and ease the risk of come down. We have rules about staying with people/going to the loo so there's no panicking about losing anyone. We monitor our water intake. Take chewing gum to help avoid the gurning. We don't drink alcohol with it or on the same day, water only. Regular small sips rather than draining a bottle in one go.
We take at festivals, certain nights out, and in the house (and centre parcs!), but not frequently. I've averaged twice a year. Each time is completely different and any time we have introduced someone new to it they have thanked us for showing them something so wonderful. It works for us and is always a real bonding experience for me, my Dp, and our friends. It's a bit less spontaneous than most users but it helps us feel safe, which enhances the overall good feelings.
I was always pretty anti drugs before. I was perfectly happy and got my kicks in plenty of other ways. I really judged people that felt the need to use it. But other things are not even close to the same as feeling true euphoria. Because of the mechanism it's just every molecule of happiness flooding your brain at once. The only people that ever say they feel like that already are people that genuinely don't understand it. Which is fine, if you don't want it you don't need to try it. But suggesting people that take it need to get a life because you get the same euphoria through exercise is incredibly naive.
Incidentally I have no interest in coke, ket, or anything like that. I don't even like weed. The only other substance I use (again, very infrequently) is LSD. Each to their own.