I don't get opioid effects from tramadol anymore either, but it's always been the quick-acting SNRI effects I've enjoyed most. It's just a great mood lifter/stimulator of interest, so I continue to take 100mg a day despite occasional concurrent flings with more serious opioids.
Before the opioid effects of tramadol faded for me, I was flying across the US coming down on acid from earlier in the morning (or last night, if you will--hadn't slept). I popped 200mg of tramadol in the airport, got on my plane and with my head against the window, I nodded for hours, dosed again and did the same after the layover. Tramadol gave me my best nod ever. It was helped by the fact that I was physically exhausted and sleep-deprived, but had I been merely exhausted, I would have fallen asleep for longer than a second or two at a time.