It's not great. The fixed armrests make the seat a little smaller, and when J reclines it can be a little tight. Middle seat IFE is also in the armrest, as are tray tables.

I highly recommend row 13, it's where I spend all my time in 319,320,321 Y. To contrast, on the E75/90 the bulkhead is actually a physical bulkhead so row 12 are great seats.