Hmm .. off the top of my head (and avoiding repetition):

Another area of improvement is the fitness center. The number and quality of cardio machines is important. We were pleasantly surprised with the fitness program on Mariner in October. The addition of consult times with the fitness director is a great step in the right direction.

Dare I bring up the laundry room? They are a great convenience for guests. I'm a stickler for packing light and won't qualify for another decade for free laundry. Keeping the machines in working order is a key driver for this customer's satisfaction.

Internet: What Larry said

Things to keep:

The wide variety of dining venues. Four restaurants is one of the reasons we'll always choose Voyager or Mariner over Navigator. Signatures is a distinctive offering and should be kept.

The loyalty programs. When they were first announced, I was skeptical. For us, they work very well. To Marc's point, consider adding an additional discount and/or free nights for those with many, many nights to their credit.

Thanks for starting this thread, Larry!