Hopefully no one will lash out in objection, but I typically do not tip extra unless particularly above-and-beyond service has been provided. My thinking is that all the staff on the ship get a fair wage, and that gratuities are also added to our fare which are (in theory) intended to provide a reward for good service. My family is neither high-maintenance nor low-maintenance, as far as I can tell.
That being said, on every cruise we've taken we have found particular crew members who did, in fact, earn extra tips from us. Sometimes it was a wonderful dining room steward who spent extra time doing magic tricks for our kids, or a Neptune Lounge concierge who put extra time into setting up a CruiseCritic meet-and-greet, or a Club HAL staff member who our kids loved, or a Pinnacle Grill manager who got us a table in an otherwise-sold-out restaurant. Things like that seem worth an extra bit of recognition, both monetary and on the end-of-cruise survey.
But for those staff members who are doing their jobs, and doing them well (which we expect on HAL), I consider them to be fairly compensated already.