we can only be grateful to have it

Rating: 10/10 (16 April 2015)

No spoilers in case you're interested in seeing what all the fuss is about but have somehow managed to avoid the actual story.
I first watched 2001 as a teenager almost 20 years ago, having understood very little, but remember enjoying the (seemingly) sparse show it offered.
Couple of years later I got into Arthur C Clarke, starting with the amazing Rendezvous with Rama (how is that not a film yet??) before getting round to 2001. Oh my God, it's full of stars! At this line I understood what that whole psychedelic sequence must've been about, so onward to a 2nd watch forthwith it was. And lo, I now got the film much better. It wasn't quite up there with my absolute favourites (yet), but understood it to be a masterful piece of work.
Fast forward 15 years or more to watching it a 3rd time (this huuuge film phase I'm having this year is thanks to procuring a HD-projector...highly recommended!).
And ye Gods indeed, it's now my Number 1 favourite film.
Older and (probably) wiser, in that 3rd watch there was so much more to appreciate: the use of György Ligeti's otherworldly music is hugely-immersive; the distinct, yet skillfully-linked, nature of each of the 4 parts of the movie feels like a proper opus; the epic presence of the monolith is fantastic, and - when you think about it - the utter vastness of the timeline is sheer incomprehensible. Above all: the film is hugely enjoyable, completely engrossing and beguiles like nothing else I've ever seen. Its ideas are as timeless as the universe itself.
As with most Great films, it's also the little things that make an outstanding impression against hugely-ambitious intention: the apes' excitement when realising they can use scattered bones as tools; Floyd seriously cutting the gentlemanly exchange with the Russian group utilising a curt "I'm afraid I can't talk about that"; the hypnotic circular weightless-walking (and running) of crew; the repeating trick of showing HAL's now-iconic red eye.
Speaking of iconism: this movie offers an incredible amount of iconic culture. If you watch this for the first time you'll feel like you've already seen it, such is its influence. And for pure open-mouthed awe we don't even have to look at the riveting psychedelic wormhole: HAL's red room scene is the one that stays with us the most.
To the 3 most common criticisms this film has:
1) "none of the characters are human/relateable enough, tho' some use this as a theory to posit this was Kubrick's intention, to allow HAL emotional room."
I don't buy any of this: Kubrick above all wanted realism: this means he wanted his astronaut and senior scientist characters to mirror the nature of their real counterparts: stoic, calm, formal. And check out Dave's stress levels later on, he's acting human alright. Plus Floyd's wonderfully-light exchange with his daughter is hardly the kind of cold, emotionless quality some amateur critics like to point at 2001.
2) "the sequences without dialogue are too long, with nothing happening. Additionally to this: the classical waltz music doesn't fit the space visuals."
I can understand this criticism, even if I never had an issue with it myself. I love those long sequences: they're enticing and mysterious, and really pull you into its world. But you either like it or you don't.
Regarding the music choices: at first viewing I also felt the more traditional classical music didn't quite fit. But on the 2nd and even more so now on the 3rd watch I really appreciate the wonderful symbiotic waltz of the spacecraft with the, very much earthbound, instruments. It's symbolic and meaningful.
3) "the film doesn't make any sense, especially the final section."
Again, another criticism which I felt sympathy with after first viewing (and back then not having read the book). I recommend anyone wanting to understand the science fiction aspect of the story to read Clarke's novelisation before watching. On the other hand, Kubrick's films are well known in their individualistic interpretation of source material. You don't have to read the book if you're happy with your own metaphorical interpretation of what you saw.
...and, as Merlin would say, that's it.
This might be my longest review...and it feels like I'm only scratching the surface with what I want to say about this monumental work. The most universally-truthful thing I can say about it is that it's not gonna be for everyone. Some of you may intensely dislike it, while some may struggle to watch it all the through. If you're one of those then it doesn't mean your taste in film is faulty, it just means 2001 isn't for you. And that's fine.
For the rest of us, we can only be grateful to have it.