I think that's kind of missing the point. You aren't really supposed to fully understand what happened at the end of 2001. You're supposed to leave the theater arguing with your friends about what just happened.
See, I'm of the opinion that "you aren't supposed to understand it" is a justification that should rarely, if ever, be invoked. I'm all for films that leave you arguing with your friends over the philosophical/moral implications, but not films that leave you arguing over the basic facts of the plot.
I know I've praised
Primer here before, and that film's certainly confusing. Even after multiple viewings, and reading stuff online, and watching the author's commentary, I'm still not 100% certain that my interpretation of the timeline(s) is the correct one. BUT the truly important part of the film—the character arcs—was discernable to me after my very first viewing.
Summary of
Primer after watching once: Two friends invent time travel. They use that power for their own personal gain. Things get confusing, but the unchecked power changes the two guys and destroys their friendship.
Summary of
2001 after watching once: Some apes use bones to kill things, and a black rock is there, too. Astronauts explore the moon, and a black rock is there, too. An AI goes crazy in space, and the last astronaut surviving has to shut him down. Then he flies to Jupiter, and a black rock is there, too. There's a bunch of pretty colors, and a weird hotel room, and a black rock is there, too. Baby in space; how did it get there?
As critical as I'm being, I actually really really
really liked
2001. Even the allegedly boring parts.