I went to this film having no idea what to expect. I actually took a date to it in the theaters when it first came out. We both thoroughly enjoyed it and it helped to have someone to discuss it with after seeing it.
I only recommend seeing this film if you appreciate non-mainstream movies. It's not as disjointed as Liquid Sky or as fanciful as Forbidden Zone. The original plot is very easy to follow. There's A LOT of subtle humor.
Here's a quick summary of the plot if you are completely lost: A big-brother type government keeps tabs on everyone in society. Suddenly a new person appears and there's no data on him (he appears insane). He may or may not be the second-coming of Christ. The over-cautious government goes into a frenzy to find him and discover his true motives. The ruler is also obsessed with immortality.
Some scenes are frantic while others are completely low-key. We follow the lead character as he encounters all different kinds of people in society.
I didn't need my consciousness altered to enjoy the film, but I know that some of my friends felt that helped.
Split was also filmed around Santa Cruz and San Francisco.