David,
As to your question "Would you tip on top of the service charge?", that depends on what % the service charge was and how good/bad the service was. You have to work really hard to get stiffed by me.
When I was on a Norwegian Cruise in February, it was Norwegian's policy to add $10 per passenger per day to your on board account. In reality, just paying the $10 per day was the "easy" way out and I am sure it alleviated the concerns of many passengers about how much and who they should tip. The breakdown of how that $10 per day was distributed was available upon request. Of course I, among others requested it. The only figure that stood out in my mind was that the cabin stewards got $3.5 per day to split among the two of them assigned to your cabin. Many people in our group chose to have Norwegian remove the $10 per day from our bill and chose, instead, to tip directly to those who provided us with a service. In my personal case, the cabin stewards got more than they would have under the structured system and the wine sommolier (if there even was such a position) got nothing from me. The only wine I typically drink comes with a screw off top. You get the idea. If you provided me with a service, I tipped you. If I had no interection with you, you should not expect me to leave you money, IMO.
Each time you ordered a drink at any of the bars, there was a service charge automatically added. Did I leave additional money every time I ordered a drink? No. Did I leave extra money for the bartenders that worked happy hour every night and went out of their way to remember us and what we wanted to drink? Yes.
That touches upon your other question whether I would tip regardless of the level of service. My answer to that is no. Truly bad service does not get rewarded. I don't just leave the exact amount and bolt for the door, though. I typically let the server know why they aren't getting anything or very little. One of my pet peeves is having to ask that my water glass be refilled. I play a little game and if the service is otherwise satisfactory, I add $1 for each refill that is provided without my asking. I'll also inform them of the rules of my game afterwards. Reinforce the behavior that you like to see.
Another of my pet peeves is dealers who don't "thank you for the bet" or thank you for an outright toke. The last time my parents visited LV I was watching my father play let it ride. He placed a small bet for the dealer. The bet lost. The dealer locked it up in the rack and never even grunted. Maybe I missed it? So I asked dad if the dealer had acknoledged the bet. Dad said no. I forbade dad to make another bet for the dealer. Too bad, in table games, all dealers suffered because of that one dealer. While on the cruise in Feb. I made a bet for the dealer. Again, no acknowledgement. Again, I thought that maybe I had missed it. The next hand I won, I gave the dealer an outright toke. He locked it up and never even grunted a thanks. I called over the pit boss and told him what had happened and told him that his dealer(s) would make more money if they simply said thank you. He said he would address it with the employee. I don't know if he did or didn't.
Maybe we are all comparing apples to oranges here. Who knows.
Bottom line is give what you are personally comfortable giving. A hard and fast % is not necessary. If I am eating a $4.95 prime rib dinner my tip is likely to approach, or exceed, 100%. If I am eating at the Hilton Steakhouse, I'm not likely to even come close to that percentage. Everything is relative.
Best Regards,
Murph