So - tipping is a more touchy subject than I thought.
I always tip what I am expected to tip in almost every situation (the exception being when I tip extra), and I don't often ask for anything special, but if I do I certainly tip extra for it.
I do try to leave something for a maid - depending on how long I have stayed and what she has done for us. I have also handed cash over to certain people in hotels and cruise ships discretely when they gave me special service.
This is just my personal opinion, but having worked with cruise crewmembers I think many of them would rather not have the tip than to have to fulfill some of the special requests I just read about here. But the better cruise lines WILL do anything to make sure the guest is happy.
By the same token, I have been on some "supposedly" top-notch cruise lines where gratuities are included and had what I would consider worse service than I have received on mainstream cruise lines. So, tipping does have its role to play.
I agree with Mike M in a big way about people who take tips off just because they can. Even if the service was "terrible" I would not do that, because you can't always put the blame on the person providing that service directly to you.