As of this moment, I haven't completed the series, so I can't fully judge about the plot and subplots. I can confirm, however, that I have been experiencing a sample of very good story writing, the past few days.
The one thing I liked about Azumanga Daioh was its older, calmer art style: no flashy colours or seizing animations but rather in accordance with some older Western cartoons. This is why I skipped on Haruhi originally but also why I was a bit reluctant to effectively start on it. Now that I did, I'm glad I have.
The more realistically drawn characters fit in with the more realistically drawn background. I think Haruhi Suzumiya, herself and Kyon look great. Especially Haruhi, whom I could perfectly fall in love with.
Rewinding the first episode on your first run for over 4 times to hear the introduction song "Bouken Desho, Desho?" needn't further explanation. The main track is superb as are all the ambient tunes which seem to be inspired by lots of styles, Indian 'Bollywood'-music, Europop and the typical Anime tracks. Sound effects are clear and never seem out of place, which, finally, unifies the visuals and audio to one solid whole bordering perfection.
Enjoyment is the other side of the coin, the infamous "Endless Eight" arc has already made a name for itself, and with "semi-good" reason. It is essentially eight time the same episode with subtle cinemato- or photographic differences, small changes in speech and music and some scenes. I am now half-way but from what I have seen from Haruhi's story, I expect the Endless Eight to end in a great climax (or not?)
Haruhi is not really suited for people who don't like anime, I think you need really need to be interested to be able to pick this up and understand it well. But nevertheless, it makes as a great second Anime to watch.
