First thing to say is that here's a very self-consciously stylish example of the European art-film of the early 60s and about a million light years away from popcorn entertainment. Presumably, if you are interested in it, you are up for for the sort of formal poetry associated with this kind of film-making and ready to engage with the narrative challenges typical of so much of this fare. If so, you can safely anticipate relishing a very tasty and fresh example in this case. As others have said, it's a little gem.
However, the hyperbole offered up by those praising it here and elsewhere is perhaps a little over-the-top. The average movie-goer of 1962 would probably have found it less-than entertaining and quite possibly annoying with it's exasperatingly elusive 'story'. It's actually a rather stereotypically poe-faced art cinema experience as parodied so mercilessly by Western stand-ups and sketch-writers looking to Eastern European entertainment. From the perspective of 2014, doubtless plenty will respond the same way too.
On the other hand, today's arthouse crowd will relish the period style and uncompromising auteur panache. In particular, the cinematography is excellent and the music and sonic character strikingly interesting. As a slice of pure period style, it's very enjoyable and distinctive. That said, it is very much of it's period, being essentially a local variation on the theme of a generational take on existentialism; heavy on the poetics and self-indulgently unconcerned with providing an engaging plot.
The director's 'playful' approach to cutting together visuals and sound in a choppy narrative is a little alienating (appropriate for the existential tone) so that, if you're not into the ride, you might suspect it to be a slow and self-indulgently obscurest trip to pseud's corner. But bear with it, and what accumulates is a bitter-sweet, coming-to-terms as our young protagonists feel their way towards some sense of their place in a dodgy cosmos. It closes in a melancholic place wherein the quest for happiness equates to little more than a striking a philosophy of accommodation. At least, that's my reading of it. It's a subtly made, fairly open-ended tale which you may pin-down differently (as I might too on a second viewing).
Hardly surprising that the Soviet censors sensed an implicit critique and dissatisfaction. But because it's essentially all expressed as a vibe rather than explicitly alluded to, this sober statement on the human condition is obviously generalised, and as relevant anywhere on the planet as in Czechoslovakia in 1962. So they evidently found it too intangible to get to grips with.
Many a viewer might too.
Though certainly not a dour a film by any means, this is a self-consciously, serious artistic statement which, in it's need to circumvent the censorship of it's time resorts to a storytelling approach which inevitably draws attention to itself. That can appear annoyingly self-indulgent at times, I found. But it also works to keep it fresh and idiosyncratic enough to reward return visits and, on balance, I'd say it's artfulness is lively and life-affirming.
Basically, though this film is not solid enough to qualify as an unreserved masterpiece for me, it is nevertheless, a lovely little treat.