Hmmm. Despite a lot of experiences with both LSD and psilocin alone, I haven't had the pleasure of trying MDxx yet (have yet to find a source I trust, don't feel like messing around with mystery pills), so I can't really speak specifically from firsthand experience. I do, however, have a reputation for knowing my drug trivia, so....
Both have been described as very intense. Different than either one alone, and more than just the sum of their parts. One notable thing is that LSD lasts far longer than MDxx, so there will be a substantial amount of time that you are experiencing the ecstasy comedown while the LSD is still going strong (unless you dose your MDxx just before the LSD peak, in which case you'll be experiencing the come-up and plateau without the benefit of "rolling").
Psilocin and MDxx have a more similar time profile, so you could take them pretty much simultaneously and be experiencing the mushroom comedown (which as you may know is often extremely euphoric in and of itself) while the MDxx is still in full effect. I would think, judging from these facts, that "hippyflipping" would tend to be a more streamlined and desirable experience -- but of course many users speak extremely highly of candyflipping as well, so your mileage may vary.
In terms of effects, I could see ecstasy assisting the user with getting past street-LSD's negative effects, although it may enhance several of them (jaw clenching and muscle tension, in particular). Mushrooms generally are less prone to side effects because they're natural, not subject to the failings of black-market synthesis as LSD is, and not likely to break down as easily as LSD either. So I would figure that again, hippyflipping seems -- to me, someone who has done neither of these -- like an experience that is more likely to be positive.
I can't emphasize enough that I'm not speaking from experience (although I hope to do both of these in the not-so-distant future), only an academic/knowledge perspective. So you should definitely look for more experienced opinions -- definitely pore over the experience reports forum here on BL, as well as those on Shroomery.org, Lycaeum.org, and Erowid.org.
Good luck and godspeed!
