Reading this report over again after discovering I can't get it in the US now that it's available (because I like to torture myself like that), it actually sounds a lot like my ondansetron/DXM experiences. I'm the only one of 3 others I've provided it to who reacts the way I do to the combo (though there was definitely a very substantial interaction with one friend in that 350 mg of DXM did almost nothing but create a state of lucidity and well being).
For me it's highly euphoric, lucid, moderately psychedelic, only mildly dissociative, extraordinarily manic, and deeply satisfying (as in the best experience of my life satisfying) -- i.e. very much like your experience of this compound. Also like your description, it lacks any confusion or amnestic effects like other dissociatives have. It's strange how similar in fact, because I have to doubt that pharmacologically anything similar beyond NMDA antagonism is going on. My best guess is that the DXM/ondansetron combo's effects are mediated through DXM's serotonin reuptake inhibition and subsequent blocking of 5HT-3 activation by excess serotonin, but that something specific about the brain's of different people makes the effects highly unpredictable (likewise, DXM's effects alone are highly varied in different people).
Of note, the interaction only occurs at doses of Ondansetron around 12 mg and the euphoria builds slowly. I typically dose a 150 mg booster with an additional 4 mg of ondansetron about 3 hours after the first dose, and it's not until about 1.5 hours later that the peak mania and euphoria is reached. It's very curious.