We stayed on the QM before our Carnival Splendor cruise in Oct 2009. She was also showing her age and needed a refurb. I know she has come under different management since them. Food was good but not fabulous - though we didn't do the brunch which seemed to bring people in droves. The highlight of our stay was watching Splendor arrive in the dark about 6 or 6:30 (our bodies were still on EST so this was not a problem.)
The staterooms used by the hotel are probably much like they were when she last sailed with a few modern amenities added (TV, iPod dock.) We did the self-guided tour but not the ghost tour.
Was very handy sailing Carnival. We walked over to do early check-in, went back for some relaxing time on deck and then walked back to the terminal at our assigned time.