Tramadol is absolutely amazing for people who don't have opiate tolerances. To me, it feels like a mixture of MDMA and opiates -- the lovey, stimulated feelings of MDMA with the nodding bliss of opiates. Imagine an opiate that makes you feel as good as any strong opiate would, but also gives you the stimulation to want to go out into the world and adventure, take walks, go swimming, and read books. At least, that's what it did for me. Your results may vary wildly.
Me and my now ex-girlfriend used to do it here and there, and had incredibly intimate experiences on it (long lasting conversations, extremely close bonding, cuddling, that sort of thing, it was beautiful).
That all ended when she overdid it one day and had a couple of seizures, which somewhat scared us off the idea of doing it again (it seemed to last in her system a while, as in, doses from the previous night carried over into the next day, which apparently added to the total amount of drug in her system, I'm assuming). If you keep the dose low and don't do it all the time, it's a fantastic, relatively-undiscovered gem of a drug. If you go overboard, it can get dangerous. Some people seem to be more prone to seizures than others.