I agree entirely with all the praise that other reviewers have lavished on these films. They're astonishing, moving, beautiful, and deserve to be seen.
However, beware the quality of these discs. They're the only ones available, so if you desperately want to own the Apu trilogy then you'll just have to put up with them; but if you can, it might be better to wait until a remastered edition. The subtitles are shoddy, frequently missing short exchanges of conversation (it's not that one can't make a guess as to what is being said, but it's disruptive to be suddenly deprived of a translation) and fading out altogether for a good ten minutes in Pather Panchali, during the theatrical sequence, so that one has no idea what the play is about or how its plot might relate to the wider themes of the film. The sound on the discs is also uneven - about 35 minutes into Aparjito, for instance, there's a sustained period of disruption - and the film often scratchy.
These are classics of world cinema and deserve better treatment. As I say, this doesn't mean you shouldn't watch these films, but patience might be rewarded if you're considering a purchase: sooner or later they'll surely be re-released in a remastered edition.