I've done DXM a few times...I'll summarize each experience below...
1st DXM Trip - it was me and a good friend, at his place...we did 2 4oz bottles each. We got the stuff down easy enough (I guess partly because we had no idea how bad it would taste and what effect it would have on our stomachs.) After downing both bottles we sat down in his room and put on our respective discmans, figuring music would take our minds off the taste and mild stomach discomfort.
My colleague says he didn't get much outta the music...me, OTOH, found it to be quite enjoyable. At one point I could distinguish and seperate each individual sound I heard. I had a much deeper connection with the music, and it was generating positive and happy thoughts. (On a side note I think listening to music really helped us settle...I don't remember having any stomach pain or discomfort while listening to the tunes.)
About an hour after ingesting the liquid we talked for a bit...I remember talking about this story idea I had about the merging of God and Lucifer (don't ask.) There were also two discernable points where I got this rush (for lack of a better word) of extreme happiness. It was really something...I wanted everyone to feel exactly as I did. I don't remember much of what I said, but my friend later told me I said something like "I'm on a direct hotline with God."
About 1 1/2 - 2 hours after ingesting my friend decided to call someand and invite him over. At first I was hesitant about this idea...even got me a little paranoid. In an instant though my feelings changed on the matter...I wanted to interact with this person while under the effects of DXM. Eventually the doorbell rang, and when I tried to get up I fell right back to the floor. After a few minutes I tried again, and mustered just enough strength to stumble into the bathroom.
I must have blacked out, because the next thing I know I am sitting on the bathroom floor, and see a considerable amount of vomit in the toilet. I assume it must have been mine, because later on (when asking about this) my friend said no one else had gone into the bathroom but me. It's freaky though because I have no memory at all of puking that much crap up...
The remainder of the trip had me crawling to and from the bathroom (to vomit) and the living room. I must say it was the strangest sensation...robowalking that is. When I did manage to actually stand up and walk it felt as though I was skipping through time. That is, if I walked a distance that normally took 10 seconds to accomplish, I would feel as though I was doing it in only 3-4 seconds.
Eventually it started to die down...I remember for the 2 hours or so before I left my friend's house I had this annoying double vision...I would have to really concentrate and focus to make anything into just one image. Luckily it went away to an extent where I could drive home.
Overall my first DXM experience was wild...it was my 2nd drug done (first being green.) The puking wasn't fun, but the overall sensation and feeling of the trip is something I will not soon forget.
2nd DXM Trip - this was with two friends...and we had green this time.
Me and the guy mentioned in the account above did 1 1/2 4oz bottles...our female companion did 1 4oz bottle. About an hour after ingesting we decided to smoke some green (to both heighten the trip and eliminate any stomach discomfort.) Even though I think it was more difficult getting the syrup down this 2nd time around, I didn't get much pain at all, and I don't think I vomited during the entire trip.
Anyways we all took some pipe hits...about an hour + 1/2 after ingesting (plus the smoking) we decided to lie down and just talk to one another. It was a very interesting experience...I felt a deeper emotional connection with my fellow trippers. (They later said the same thing.)
From what I remember we spent the majority of the trip just sitting and talking...I know we had some pretty bizarre conversations (including one about liquifying dead people which I'm still trying to make sense of.)
Overall this was a great trip. I think the green really had a positive effect. Although there was less "otherworld-liness" than the first trip, this one was more social. Even though I have always aimed for the higher plateaus this trip showed me lower level ones can be fun too.
3rd DXM Trip - I was with the same two people this time. The female tripper settled on 1 1/2 4oz bottles, while me and the other guy decided to go big and do 2 1/2 4oz bottles. Like last time we got the stuff down (and let me tell you...2 1/2 bottles is TOUGH.) IIRC we waited about 10 minutes and started hitting the pipe. About an hour after ingesting (and several hits each) we all found a comfortable place in the room, sat down, and relaxed. Like last time we planned to just sit and talk, and see where the trip took us.
We didn't do much talking though. From what I remember it seemed I was shifting into other realities...one moment I would be in the room with the other two trippers, and the next I would be somewhere else entirely. I remember one of the realities was on a ship in the middle of the ocean. Another was either in my old high school or in my current place of employment (it could have been both...my memory of this trip is somewhat hazy.)
In any event I spent what must have been 3-4 hours in this trance, going back and forth between the realities my mind was creating and the real one. I know at one point, while jumping back and forth, I was trying to distiguish which reality was real...I can vaguely remember asking people, in each reality, if it was really real or not. Wild stuff.
Eventually we all recovered...both my friends can't remember a thing about the trip. Sucks for them. This is the closest I have ever gotten to the 4th plateau...if nothing else this trip psyched me up for a true 4th plateau trip, like the ones I read about on the net.
4th DXM Trip - This was with the same two people as in the 2nd and 3rd above trips. I'm pretty sure I decided on 2 4oz bottles...I think the guy did 2 also and the girl did just 1. Immediately after ingesting the syrup (this was by far the most difficult 2 bottles to get down) we all started taking bong hits (mainly because all of us were feeling stomach pain...me and the other guy moreso though.)
About an hour after ingesting we had all taken about 4-5 hits...I thought it would be enough to mask the pain and discomfort that I knew was still there. I was wrong.
About 5 minutes after putting away the bong I rushed to the bathroom and began puking. In all I must have puked like 15 times, over an hour or so period. I remember sitting there in the bathroom floor, feeling the layers of sweat on my head, and trying not to choke on my own vomit. It was definitely a very unpleasant experience. (I also remember seeing the other guy puking into a wastebasket several times...guess it was too much for him too.)
After about an hour and a half of hell in the bathroom I went back into the bedroom, hoping to relax and salvage something positive in this trip. It was not to be though, as I got one of the worst headaches in my life while everyone else was sleeping (not long after I came out of the bathroom I think we all considered the trip to be a bust, so we all decided to just get some rest.)
Overall a negative experience, and that's putting it lightly. I admit I am a bit reluctant to do DXM again (I haven't done it since) although I think the syrup is the reason for my hesitation...the stuff seems to taste worse every trip.
In any event, when all is said and done I would recommend DXM...when everything goes well the trip can be really spectacular. I would though recommend having some green present to alleviate the stomach pain (more bottles = more green.) Also try not to eat anything for at least 8 hours before the trip. If memory serves correctly that 4th disaster trip was the only time I had a meal within 8 hours of ingesting the syrup.
When all is said and done though, I'd recommend doing DXM at least once. Just make sure that first time is done right, or you'll be sorry.