These were *gobbled up*! I'm making two dozen next time. Things I learned: 1) Slice the eggs with a COLD knife - it just cuts easier. 2) REALLY DO NOT MAKE THESE AHEAD OF TIME. You can cut the eggs and arrange the whites, and put the yolk mixture in a bag, but don't pipe it out until you're ready to leave for the party. I didn't have great problems making them too far in advance--I just covered them with damp paper towels--but it would have been easier just to wait.
Also, I like to vary the eggs in the batch, so I top them with different things -- some with herbs, some with chopped shallots, some with paprika, some with chopped bacon or a thin slice of radish. Mix and match!