I never got around to watching it when it came out, and I think I'd completely missed the critical reception and box-office failure it received. Which saddened me to read after the watch, I have to say, as I was really happy to have watched it.
For those who don't know the film, I personally liked Roger Ebert's review (with whom I generally vibed). It was polarising, and genuinely confusing if you want to "understand" a film, while also potentially being vacuous and overwrought. I'm not going to say it was a good film or recommend it to people. If it's for you, you'll know. All I'll say is that it was, for me, a very good kind of film and generally well executed. Some ambitious film ideas and high level or broad concepts put to screen pretty full-throttle.
I haven't seen a film in this general category of viewing experience for a while (probably entirely on me). Last probably would have been 3000 Years of Longing and maybe Twin Peaks S3 (I count that as an 18 hr film), and then Aronofsky's The Fountain (to which Cloud Atlas is probably the closest sibling I can think of).
Without getting nostalgic about films or critical of the current era (I'm not on top of film enough to do that) ... I was certainly reminded that I need to revise my film/TV diet. It re-affirmed for me a sense that films are more powerful than TV and that this era of TV has been productionised in a way that seems to suck the art of it.
As for what the film was actually about, I think it's much like 2001 A Space Odyssey, it's both obvious and confused/inexplicable. I'm sure there's a whole technical breakdown one could read or endeavour to create oneself, but I'm happy to have watched it once and perhaps revisit it again later to try to pick up on all of the connections I'm guessing they wove through the film, in large part because I think that's in line with the spirit of the film which I'm happy to embrace.
Beyond all of that, but kinda connected I think, was to reminisce about the Wachowskis' career, where whatever their flaws, I think I prefer them making things to not ... there's a certain essence of good-hearted and ambitious geek-dom to their stuff that I'm just happy to watch (including Jupiter Ascending and Matrix 4).
I don't know, after reading the book the movie is a bit hard to watch. There is a lot missing from the movie, small nuance that goes a long way to making for a much deeper experience.