i've done it. i really liked it but i did it at home which was confusing trying to mimic a tape with no instructor. i always felt sore the next day. also the ideas of a snake goddess shooting up my spine too mate with a male god in my head is kind of freaky...
however i love the more liberal ideas about simply opening up the chakras and unifying your energies with universal pure and good energy. it's a fun idea, and i spent a good amount of time studying them and their workings. although for me it always comes back to: did the buddha teach this? what would he say about it?
and that shatters the fun chakra ideas for me, he likely would have shut them down if his followers were practicing for these purposes. i imagine it going something like:
"what do you think [insert name], are these energies permanent or impermanent?"
"and what are things that are impermanent?"
"therefore [insert name], you should let go of anything that is not permanent since it is not yours." and so on and so on.
however the purely physical aspects of it are GOLD and i really wish i had the time too go find and take a class to learn them. from what i hear, people who are good at yoga have very few back problems and are generally healthier than more stagnant people.
i practice qigong since i know it already and it's much less strenuous (which likely means it's not as wonderful at getting you stretched out and fixing aches and pains), there's only three energy vortexes! much easier too remember, and the exercises are super easy, which again probably means it doesn't work as well if i had too guess. however it seems qigong would be good for an older person or someone with joint problems who cannot be so flexible. i have the same problem with hearing the buddha's fictional sutta in my head about the energies but i just tell myself i'm simply using positive thinking for better health
someday i intend to get into yoga seriously as it's always interested me.