Auto-tips are a two-edged sword. They nearly eliminate service crew being "stiffed" altogether, but on the other hand, they don't get to keep all of it. It's my understanding that auto-tips are "pooled"-- i.e., put into a big "pot" and divvied up about a thousand ways on a Panamax-size ship-- not only among the "frontline" service personnel (dining room waiters and room stewards) passengers interact with daily, but also lots of behind-the-scenes people passengers never see-- kitchen staff, laundry workers, etc.
Accordingly, I always give my waiters and room stewards something extra in cash, in addition to the auto-tipping. These extras are revenue they DON'T have to share with anyone else, and they always appreciate it greatly. Considering the long contracts, hard work, and unrelenting working hours these guys have to deal with, all while displaying a smiling and positive attitude, I consider it a small price to pay. If you're anywhere near as impressed as I am by the graciousness and commitment the crew bring to their hard jobs,I would encourage all my fellow passengers to do the same on lines that use auto-tipping.