Well that was great The animation was really beautiful throughout the whole series although the last episode certainly crowned the whole thing.
I wasn't such a big fan of the mystery theme but I really liked two other things: the dialogue and attention to detail. The drama was very down to earth (if there's a second season I hope there'll be more of it though) but I guess that only emphasized the smallest things. Some of those little insights were great too:
My favorite bit was how Mayaka felt bitterly envious of authors much more skilled than her, especially since the author she adored the most wasn't even a manga fan and just wrote that "masterpiece" for fun. Instead of the usual Bakuman bullshit, Hyouka offers no meritocratic illusions. Now that's something I wasn't expecting. Well done
Satoshi was my favorite. Definitely not a one-dimensional character. Cheery on the outside but a little bit tragic on the inside. He was a lot like Mayaka in the sense that he was also aware of his limitations. I liked his monologue in ep 21 about him always holding the second place, never being the best in anything, and being afraid to commit to anything.