I guess it strongly depends on the airline.
What I found excellent was that you could tell the air-hostess when you wanted dinner served, so that I could finish up the last alterations to a presentation I had to give the next morning and then have dinner (as opposed to getting interupted by dinner in business class).
And premium lounge access, but I guess that one is usually well advertised.
From (limited) experience, it only justifies the ticket price when doing multiple long or medium haul trip legs with relatively short (1-2 day) stopovers.