Severely depleted serotonin levels, causing irritability and possibly depression
Loss of focus, concentration, and attention (good luck programming competently the day after)
Bruxism (jaw clenching/grinding)
From a wide array of experience, pure MDMA (in recommended doses, meaning 200mg or less) produces less of a hangover than two beers, with a very real "afterglow" which lasts for days after. Excellent focus and concentration included.
This is a good read: http://www.cbc.ca/news/canada/british-columbia/pure-ecstasy-...
"The drug's letdown can include feelings of confusion, irritability, anxiety, paranoia and depression, and people may experience memory loss or sleep problems, jaundice or liver damage."
And:
"Dr. John Halpern, a Harvard Medical School assistant professor who led the research, said pure MDMA can change core body temperature, heart rate and blood pressure in the short-term, and decrease immune resistance for a few days."
Sounds like a hangover to me:
"2a : disagreeable physical effects following heavy consumption of alcohol or the use of drugs" http://www.merriam-webster.com/dictionary/hangover
I'm not saying MDMA is terrible for you, but it certainly does cause hangover effects (and of course, this will vary by person).
1: http://www.ncbi.nlm.nih.gov/pubmed/15212815 2: http://onlinelibrary.wiley.com/doi/10.1002/1098-2396%2820010... 3: http://www.ncbi.nlm.nih.gov/pubmed/10619665 4: http://www.ncbi.nlm.nih.gov/pubmed/11931860
This happens when MDMA is cut with meth. I think he mentioned "pure", but when it's illegal it's hard to guarantee purity, so legalization would have at least that benefit.