Why do some people say speed isn't good?

So, I just tried speed today for the first time, I have seen lots of people saying that it's not good or not worth trying, but for me, I had one of the best highs I have ever had, I would even say it's better than MDMA in some aspects, if you are thinking about trying it, I would recommend it. But the question still stands, does speed not affect people the same or what?