Great place to go if you enjoy having a drink and singing some songs. Or listening to a bunch of people enjoying a drink and singing some songs. The music is as good as the people request it to be... name your tune (on a napkin), add a dollar bill, and drop it on the piano... then hope someone knows how to play it
And yes, Cast night (Sunday? Monday?) is a great choice... the more people the better.
Definitely a fun place to go. I think there is a cover charge. My wife and I went a few years ago when we were in our early twenties and we had a blast. It is more fun when there a lot of people inside, so don't go too early in the evening.