I watched quite a bit of streaming before making up my mind and honestly it's really cool if you're into RPGs with a good story! The gameplay is smooth, the combat is dynamic and there's tons of stuff to explore, so you can easily lose track of time for hours (in a good way).
As for how long it takes, it really depends how you play - if you just do the main story straight through it's maybe 30-40 hours, but if you do the side quests and mess around a bit it's easily double that. The mixed reviews you see on forums are often because some people think the dialogue is too cinematic or the choices aren't impactful enough, but honestly that style really gets me going!