My one experience with this compound was probably the worst body-load/unpleasant side affects from the 2c-x's I've tried (c,d,i,t-2). I took a bit too high of a dose for my first time, 12mg, but it was interesting and quite unique. Despite the side affects i found it useful, and it has potential in terms of getting something useful/learning from the experience.
The over-stimulation, muscle tension, gastric disturbance, and other side affects just kind of turned me off from it. If you do try it, start low, by low i mean under 10mg.
I plan on trying it again in the future, but for the moment its shelved in favor of novel 4-subb'd tryptamines. I do like how it feels less recreational/hollow, and more insightful than the other 2c-x's though. But i can get that from 2c-d or t-2 without so much side affects.
IMHO, its worth a try, some people love it, but its seems more volatile in how people react to it than the rest of the 2c gang. I agree with shulgin that its difficult, but worthwhile. People tend to underestimate how difficult going into their first experience though, at least i did 12mg caught me off guard. There's potential there though.
And finally, I've heard a few reports from nexians, and some other reports scattered on various sites that 5ht-3 antagonists help make it more bearable. So think lemon oil, ondanserton, ginger, etc.
Just be safe, i would say 20mg is a reckless first time dose assuming you plan on taking the whole capsule. Its far more potent than any of the other 2c-x's ime.