I have ridden 6500, 6600, 7700, 7800, Campy 9, Campy 10, Rival, Force, and Red. I had the chance to try out 7900 last week for a bit. My favorites list for shifting is probably....

1) 7900
2) Chorus / Record 9 speed
3) 6600 or 7700 (7800 is too smooth for me)
4) Chorus / Record 10 speed

The 7900 stuff takes it to a new level IMO. I was really impressed with the precision and feedback of the shifts. Too expensive for my blood, but nice. I didnt get to ride it long enough for an ergonomics decision, but it felt pretty good.