Still haven't beaten it yet, just been slowly going through it on the weekends mostly. But I just got through Byzantium and the "big decision". I did find something yesterday that was just a nice little semi-hidden thing not associated with a quest but hit me pretty good and hard.
i'm basically in the same boat, seems like the only time i have to drop a chunk of hours at once is once a week, but thats fine pacing for me. i am pretty sure i am about to do the 'big choice' you are talking about (or just did) on sunday. that spoiler-ed story is awesome and makes me worried i may have missed some stuff like that...i know theres been times when i loot a 'special' armor/ weapon and don't notice why its different or named in my inventory. who knows who i may have murdered