It's odd you mention this. I was heavily addicted to tramadol for a good 10 years. Other opioid users pretty much laughed at me, but I swear on my grave, for years I received a very heroin-esque high. It started off very stimulating (more productive than amphetamine 'stimulation') and then slowly faded into a noddy dreamy state after about 3 hours in (which is around when it finished metabolizing). I nodded hard and was SO euphoric every time I took it. This lasted for years. I couldn't understand back then why people hated it so much.
But then after getting into morphine, heroin, fentanyl and buprenorphine a few years later, it seems like my tramadol has stopped working. I thought it was tolerance but even after some absence, I still do not get those AMAZING effects from tramadol like I use to. I mostly get the serotonergic nausea and tingling in my brain like I'm about to have a seizure. No nodding, no extreme euphoric or enhanced appreciation for music (which was my favorite past time, getting high on tramadol and collecting and listening to the most obscure and crazy underground music I could find). I use to sit and nod and listen to my music for hours and hours and never get bored. I put so many burn holes in my blankets from nodding out & listening to music. Of course it's been awhile since any opioid gave me this powerful euphoria and lust for my favorite music, but I've always wondered what happened to me and my beloved tramadol. Now the only opioid I really crave for is heroin.