If you have seen Air, this has much less depth to the overall story, but works much better as a moefest.
If you have seen Kanon, this is similar, but is far more down to earth, with less supertnatural aspects to the stories, and more normal day to day school stuff. Also, the girls don't mysteriously disappear from the series when their story is done.
If you haven't seen Air or Kanon, watch one of the three to see if you like Key VN adaptions.
Don't bother with other VN adaptions, as they just don't compare.
Don't bother listening to /a/, as many people who dislike these series are intense faggots who will RAGE until they expire at the smallest mention of them.