I have stayed there many times and really like the Delta King for a number of reasons, chiefly among them is the bar and restaurant which you must visit if you stay on the boat permanently docked in Old Sacramento. Be absolutely sure to make time to stroll right into Old Sacramento which is truly an amazing spectacle itself. That close proximity to the amazing restaurants and such is a main selling point to staying on the DK (Delta King) and staff are friendly and professional. Late checkout is never a problem when asked for in advanced (I always ask for that)..
The rooms come in a variety of sizes and amenities. Some rooms are smallish and if you get a 2nd floor room they will be short as well with low ceilings (I'm 6'4" and had to duck to go to bathroom), so when you book a room be SURE to ask for 3rd floor if you are tall. Also they have a few suites which are booked for when they host weddings etc., or just a super nice weekend for those who secure it in advance... those rooms are in demand I'm told.
The breakfast is excellent and everywhere you go on the boat, you really get the feeling of what it must have been like to float with her down the river with gamblers, ruffians, and business people on their way to San Francisco or Stockton a hundred years ago. Be sure also to take a little hike to the top deck and catch a view of the Tower Bridge and a bit of a bird's-eye of Old Sacramento... You'll be glad you did!!