Even those who do not like Buñuel's "Un Chien Andalou" will probably never forget it once they see it. It's one of the weirder and more interesting films that you'll ever run across, and even aside from its significance, it would be worth seeing for the distinctive style and material.
It is also very well-crafted, despite its apparently chaotic narrative (or lack thereof). Even when it is impossible to attach meaning to some of the images, it seems clear that it has been filmed almost exactly as Buñuel and Dali intended. Even the music seems to have been chosen deliberately, and at times it complements the images surprisingly well.
While the exact meanings of many of the symbols are probably deliberately obscure, it strongly suggests some general themes such as desire, frustration, and the like. To attempt to analyze it carefully is almost certainly a mistake, and it is probably best taken as a dream or a dream-like series of events without the kinds of obvious connections that one might want to find.
Likewise, it's hard to determine just how good or how important it may be. The extreme disregard of cinema conventions is hard to evaluate now, in that the movie itself established some alternative conventions of a sort. The images themselves are often fascinating, sometimes unsettling or even off-putting, almost always interesting and suggestive.
Perhaps the one thing that can be said about such a movie without much risk of going astray is that almost anyone who has a real interest in cinema or cinema history will (or ought to) want to see "Un Chien Andalou" for himself or herself. Hearing it described by someone else really cannot adequately convey what it is like.
