This "review" is a bit long, but as I enjoyed other reviews that included lots of info and tips, so too will this review.
My wife and I sailed POA with our 2 sons (20, 18). We had 2 inside cabins on deck 4, midship, center. We experienced almost no motion. My youngest son is very prone to motion sickness and was queasy anytime the ship was moving except in his cabin.
TIP #1 Cabins 4063 - 4081 are great for motion sickness. They're also close to the midship stairwell down to the deck 3 gang ways or the stairwell up to deck 5 for customer service, the shops, and the Hollywood Theatre. Deck 4 is also the bottom floor for the elevators, so they're empty when they pick you up to go to deck 11 et al.