Had my first 2-class upper deck Y experience the other week, and definitely noticed the narrower overhead bin compared to the lower deck. Had to rotate the way I store my backpack in the overhead.

While the side bins are great (for the person who has the window), the alignment with the Y seat seems to vary - for the bin slightly in front of me, if the person in the seat in front uses the bin cover as an extended arm rest, then I can't open the bin; the bin right alongside the seat also extended behind a little, so by the same principle the person behind could open it if I wasn't leaning on it. And the smooth flat surface running the length of the cabin did mean that someone's phone that was resting on top of the bin covers went 'whoosh' and slid through a few rows upon take-off!