What can I say about this movie that has not been said by all the other comments here, they pretty much sum up everything, the people who love it cherish it, the people who hate it... well, they loathe it. This is the movie equivalent of Marmite.
I personally have committed every second of it to memory, it is cyclical, claustrophobic, introspective, magical and stands as being one of the most unique films ever made. Despite what many have stated, I believe this truly is a cult movie, it is a diamond in the rough just waiting to be discovered, once unearthed it's fantastical psychedelic visuals and incredible soundtrack will be unforgettable, which is an achievement in itself. One of my friends who watched it likened it more to a musical, and in many respects to those who do not fully appreciate the context in which this film is made, would probably get more out of it to view Head as such.
I was always fond of the Monkees, especially the T.V. show back when it was repeated during the 80's. My mum had recorded Head for me when it was shown on T.V. late night, as she knew I liked them, I watched it a day later and it lodged in my memory until I was able to find a copy on DVD about 2 decades later, what I would love now is a special edition, it would be fascinating to get a greater insight into the making of this masterpiece. We can only hope.