DW and I are about to do our first Celebrity cruise. We've done Disney, RCCL (2), HAL (2), NCL, and Carnival.
We pre-paid our gratuities for this upcoming trip. Based on what I've read in this thread, we're ok to assume that's good, but it would be a good idea to keep back a few hundred in singles, fives, and tens to keep the wheels of service well lubricated.
All the other cruises boards have the same robust discussion about the tipping culture on ships (as I'm sure you all know). I'll do it because it's what's done, but I do think it's disingenuous of the cruise lines to not give customers a full picture of the costs of cruising.
Rock on rockers! 🙂