I used to LOVE sucking on an actiq while rolling... Fentanyl is only 25% bioavailable orally, although it is 75% bioavailable bucally (through the gums) [source:
www.actiq.com ]. In my experience opioids add to the pleasure of physical sensations while rolling, and reduce one's anxiety, without significantly affecting the empathogenic effects (the main reason MDMA is special). However, not everybody experiences opioids as pleasurable, and many people experience nausea from them. Generally opioids are more subtle than other drugs, and are often more expensive to get high on than other drugs. Of course the greatest downfall of opioids is that given a steady supply practically everybody will be drawn towards using them daily, at which point the user NEEDS them to avoid extreme pain and suffering (not fun).
From my experience fentanyl is not very desirable as far as opioids go, due to its high cost and EXTREMELY SHORT duration (30 minute high, back in withdrawal in 2-4 hours), but I wouldn't mind coming across small pills containing a known-dose of it and nothing else, because they would probably be a lot of fun to snort or smoke... The MDMA content would preclude any such usage, and the unknown dose renders it dangerous.
It is accurate to say that it is many times more POTENT than heroin, but this does NOT mean its effects are going to be stronger at an equi-analgesic dose. Potency is only a measure of the relative size of an active dose of a compound.
There is no reason small doses of oral fentanyl should pose any additional danger when combined with ecstasy, however the sad fact of pressed pills is we do NOT know how much is in any given pill, or even whether they contain the same dose. I had a friend die from injecting a fentanyl patch, so it does have lethal potential.
