I split a 100mg sample with a mate @ Glastonbury. It was nowhere near enough of a dose for either of us but we both recognised that it was potentially going to be very interesting at higher doses. No visual stimulation for either of us, music appreciation was heightened, both became very chatty at t+1.30hrs.
At t+3hrs we both also took 2 pills which were more or less definitely pips, at which point a lot of good stimulation kicked in (just as the The Orb played, perfect timing). This made the experience more like weak mdma, but very enjoyable. The pills were ones which we both had used before and after with no bad effects (I tolerate pips very well, no comedown or usual shittiness associated with them).
However, at t+4hrs I then started to experience a persistent kidney/stomach pain which pretty much killed my night off, and made me want to sleep. I had to take 2 x 500mg of paracetamol to fight the pain, which seemed ineffective. My mate had no ill effects at all, and remained on a higher plateau than I all night (despite being 2 stone heavier).
No stomach pain or comedown the next day, and nothing the days after. In fact felt pretty good.
To summarize, 50mg was way too low a dose for us both - 12st/14st males, long history of various substances, both fit and healthy. We had neither of us caned anything else the day we took it, and were on normally filled stomachs (ate lightly about 2 hours prior). I would like to try it at 100mg as I could clearly tell that the 'handshake' I got off 50mg suggested very interesting potentialities, but I would be apprehensive that it would recreate the stomach pain, which was pretty unpleasant.