Tachikomas are awesome... I only wish their little Omake theater bits at the end of the shows had been translated in the version I saw. Their growth throughout the series is one of the most underrated aspects of the whole thing... they basically grow from robots who parrot humans to learning to be self-aware and have wants and needs and figure out motivations and question the nature of their existence... it's really quite a remarkable sub-plot. Intellectual all while being very cute and very very funny.
Innocence is VERY dark and depressing, but visually stunning. I can also see where people might think the series sacrificed entertainment value for obtuse intellectualism, and hold it against the show, but I watch plenty of pure entertainment series... having just one be really smart... even if it gets a bit overbearing, is refreshing to me.
ANother amazing series for the anime fans out there is Vision of Escaflowne. Quite possibly the best animated television series ever made. I say that with no sarcasm or overstatement. It is a single season, 26 episodes, and there isn't a single moment of filler in the entire thing. It's like a 13-hour movie. Every character, even minor ones you only see for a couple episodes, is sympathetic. Every one, from the heroes to the villains have rational motivations... even noble ones. Noone is all good or all bad, everyone has nuance and you like every single one (even if you also hate them). I cannot recommend the series enough.
Interesting side note: Yoko Kanno, the one who did the GitS: SAC music sampled earlier, who also did Cowboy Bebop (she's in the red jacket), also did the music for Escaflowne. Example. (scenes there are from the movie, not the tv show... the two are only marginally related and while the movie is good, it doesn't come close to the show) As you can see, three completely different styles in the three shows, all the same composer. She's one of the most impressive and versatile musicians I listen to.