I was on the March 19 sailing of the Constellation...so this is a first hand report...
They had one "White Nights" Ball - Masks required, white apparel requested (to aid with the lighting effects)..."House" dance music, pretty loud...
The other nights, it is basically just a weird bar...with weird entertainment...
Rather than having, say, music and dancing...or karaoke...or a piano bar guy...they have a number of lighting effects and strange music and several costumed characters are introduced, one at a time, do some schtick onstage and then wander around the room, individually interacting with the patrons...
Don't think of it as much as "entertainment" as it is an unusual place to hang out...
You are either going to go "huh? what the heck is this and why am I wasting my time?" or you are going to think "Cool. Different. Let's hang out there and have a drink"...
But don't think of it like you're going there to watch a circus...