shugenja speaks truth, or at least not total nonsense as everyone is claiming. Obviously nobody is advocating you pop a 150mg cap every night with your multivitamins here, this is SMALL DOSES we are talking about, below those typically seen with MDMA usage.
Those who are insisting that, blanket statement, MDMA will increase your tolerance massively and leave you impotent et cetera - I have tried something quite similar out of youthful folly, and found that low-dose MDMA (at least when plugged) has a very different headspace and feeling than "supra-threshold" doses (>60-80mg usually for me - I tend to stick to plugged over oral MDxx for reasons of dose efficiency, it's almost twice as effective per milligram when taken non-orally.)
It's almost a functional stimulant at that level - no gurning, gunned pupils, and teeth grinding, but there is definitely an effect present. It is not a "drop in" amphetamine substitute (you want that, try 3-FPM) and I didn't take it for long periods of time (maybe 4-5 days?), but I did notice that low doses facilitated usage on multiple consecutive days without too much tolerance developing. I kept it to one dose per 24h though, never exceeding 50mg.
Animal studies showed that as a stimulant, MDMA was something like 1/3 the potency of amphetamine, and didn't substitute entirely, so again... this sort of makes sense mechanistically. The PK of amphetamine usage at very high doses is way different from amphetamine at 5-10mg a day, but nobody claims taking amphetamine at 5mg/day will cripple your DA system.