I suggest you watch this documentary:

http://www.youtube.com/watch?v=yt6PHhOZ32g&search=mdma

It was run on ABC (hosted by Peter Jennings), and deals pretty honestly with the science of MDMA. The honest answer at this point is that we don't know what the long-term effects are, but, when used properly and not in great excess, it appears to be extremely safe. In my opinion, it is similar to mushrooms in that it should be respected and not seen as merely another way to get "fucked up." Before it became illegal and gained popularity as a dance/recreational drug, it was primarily seen as an empathogen and was used more for personal discovery and development than for fun (although it is very fun!).

To clarify, using it just for fun isn't inherently evil - that kind of reasoning is just silly - but purely recreational users tend to use more of it more often, which increases the risk of physical harm. It's your body; be careful with it. That said, it's tragic to see the disgusting lies purported by authority figures working so well with MDMA, even amongst people who have realised that similar lies about things like pot are, well, lies.