First the good: the itinerary was spectacular, and we all had the trip of a lifetime. We also liked the mid-sized ship... It had everything you needed, but was easy to get around.
So... Why 3 stars?
A bit of background: our group of ten is not new to cruising. We've been (multiple times) on Royal Caribbean, Princess, Holland America... And two of our group has been on Crystal, Azamara, and (yes) Oceania before. And so when the rest of us who had not yet done the "luxury cruise" experience came on board, we were excited to see what the difference would be. Particularly as this cruise was given great promo as the "inaugural" cruise of the newly renovated Insignia ship (the owner was even on board!).