I had what I believe was methylone last night. It was sold as 'MDMA caps', but due to the effects I doubt it was MDMA. The powder was a slightly yellow white, with small crystals.
The effects did have quite a few similiarities with MDMA ie. eye wobbles, enlarged pupils, jaw clenching. I also got a 'munted' feel but not as strong as MDMA gives. a more dirty messed up feeling. It was quite empathetic, and I spent alot of time chatting to randoms. It is also gave a more lucid high than MDMA, I find often on MDMA I get a bit scatty in conversations, not so much with this. It lacked alot of the amphetamine type qualities of MDMA, now where near the same desire to dance or energy lift. Duration isn't as long either.
One bad thing about it was the ridiculous amount I sweated on it. It was hot in the club, but the amount I sweated got me worried for a bit, as it was really excessive. died down when I went outside though.
As a substitute to MDMA it isn't bad compared to other things. Shits all over BZP and MDPV. I would put it on par with mephedrone. less fiendish, longer duration, but not as good to dance on nor does it make you as excited.
Comedown is better than MDMA, but methylone has a worse come down than meph.