Our 18th cruise, the first aboard Oceania's Regatta. We prefer smaller ships (under 500 passengers) but she was fine at over 600. Intimate enough, and we'd book on her again for appealing destinations.
Pluses are her service and food. Staff is congenial and promptly helpful, ship is spotless, cabins are nice but not spacious, highly touted beds are very nice but not that big a deal. Meals are excellent, and you can eat as much (or little) as you like.
The Regatta is excellent, but does have its flaws.