Gave this one a spin yesterday. It was my first dissociative in about a year or so, picked it up along with some MXE. First I took a cap of 75mg which kicked in surprisingly fast and left me in a very laid-back, yet definitely dissociated state within less than an hour. The effects were very mellow and non-manic compared to MXE or 3-meo-pcp, and felt a little on the "softer" or "jellier" side, akin to how I might describe a medium dose of K. My speech was barely impaired at all, but I definitely started to get the fuzzy 'amnesic' effects which others describe. At around the 90-minute mark I vaped roughly 25mg which definitely kicked the trip back up a notch, but only really served to extend the peak slightly at that point.
After about 2-3 hours I felt myself getting pretty close to baseline (which was very quick compared to MXE, though in retrospect I'm not sure how close to baseline I really was...) and felt safe to bump an equal dose of MXE. This rapidly led to the confused, couch-locked state I'm all too familiar with, and in general left me as a bit of a blob. I was still somewhat lucid, it just required all of my effort to think straight. In the future I probably won't combine these substances, and am not sure why I did in the first place. I guess I'm just seasoned enough with dissociatives that I felt fairly safe doing so, and at no point did I feel at all in danger or psychotic, but still it was a bit much.
To me it felt very "clean" or benign, almost moreso than MXE or 3-meo-pcp. I have minimal experience with dxm, which always felt very "dirty" to me, so I'm not sure where all the comparisons to that come from. Perhaps it's just that warm jelly feeling. All in all, from what I remember, diphenidine seems like a very worthwhile substance. I found it much more warm, easy-going and "chill" than nearly any other dissociative I've tried, and will definitely be repeating the experiment with a similar dose sometime soon.