Kanon 2k2, as hideous as the designs were, actually had a pretty nice pace going on. Some might call it rushed, but I easily absorbed everything even as a junior high aged underage b&. Kanon 2k6 might have its pretty pictures, but it told almost the same amount of story in twice the time. Most of the screen time was spent on useful 'character development' moments like Shiori telling us how much she likes ice cream.
AIR might have changed a lot from the source material, however I don't really care since I haven't checked the VN (and don't plan to). However, with the what I have, I do feel that the movie was a far stronger stand-alone story than the series, which I thought was a narrative trainwreck (Yukito turns into a crow?).
I dropped Clannad because I felt it was too similar to previous Key adaptations, so I will refrain to comment on that.
All that is left for me to see is the movie.