Yeah, it was one of those movies that in the cinema was a bit of a visual overload... The main reasons I went to see it was a) at the time Ken Russell was one of those directors whose work intrigued me... mainly because of his TV work on the old Omnibus series. Song of Summer comes to mind straight away and of course, Tommy and The Devils also contributed to the mix, but it was his imaginings on Liszt, Mahler, Debussy etc that drew me to the film.
b) involved drugs!
As for Altered States itself. I was captivated by the images and the story about using sensory deprivation to achieve a heightened sense of... well self I guess... Although as I recall there may have been some local psilocybin involved at the time of viewing!!