Hmmm, a few things to say here. Firstly, as a matter of simple fact, the suggestions by Shrimp and Mare-C that acid might be laced with some other substancce, or even be another drug entirely, are baseless. LSD is an incredibly potent drug, you only need a tiny amount to get whammed. I mean, imagine a piece of paper dipped in orange juice and then dried - how much of an orange juice experience would you get? Yet with LSD that's quite enough! The thing about strychnine being used in the process is also totally untrue as well.
With E or speed, you need a much larger amount, so it's easy to cut with shite. Acid is nigh-impossible to cut, and as it is ludicrously cheap, any substitiute drug would be more expensive! The only way to rip someone off is to sell them a piece of paper that's not been dipped.
Mare-C's worry that it would be a tad hypocritical to use such a synthetic product is wayward too. Right now you're sat in front of a keyboard made of unnatural synthetic plastic. And what degree of bizarre processing goes on to turn soya (a *bean* for fucks sake!) into ice cream or rashers or whatever? But I suspect most of us happily munch away. Synthetic/natural really isn't an issue. Also, you're consuming a miniscule amount of LSD; the issue is not to do with metabolics, it's to do with psychology and spirituality.
Personally, I love acid. I do it very rarely (not at all so far this year, in fact), but if I were on my death bed it would certainly rank in the Top Ten Things I'm Most Glad I Did. The randomness and uncontrollability that makes Mare-C wary is precisely what I adore about it. Anything can get weird, or easy, or captivating, or beautiful (when else would you spend half an hour blissed out staring at a rusty car bonnet?). There is always a feeling of potential scareyness and absurdity, which adds to the alert excitement for me.
That said, it's not *totally* uncontrollable; you get so reactive to your environment that a change of place/music/thing you're playing with in your hands/lighting can steer it very effectively.
Some people with mental health problems have even found it to be useful (it was initially used to treat severe alcoholism), but there are also a lot of people for whom it's been the trigger for their latent problems. Like any thing that involves psychological and spiritual journeying, some people come out enriched, some find it disturbing, and a few get very damaged.
Respect for the drug is important. That's not to necessarily susbscribe to the 'use/abuse' distinction; certainly I'd take issue with Mooncat's idea that necking a load at once is abuse. It depends who's necking it and why.
The acid experience is as individual as the person taking it. The best thing I heard about the after effects was in Paul McCartney's 'admission' interview from the 60s where the said that it opened doors for him, and that whilst he could have reached the feeligns and ideas by other routes, acid is what did it for him.
Not one to do every day, but for me it's the one I've got the most from in terms of opening my mind, and in terms of having a right laugh.