Hello OP,
I am on the MS Endeavor in Antarctica right now on a Lindblad/National Geographic tour and it is fantastic. Spent NYE in the lounge and it complete daylight.
We are in the middle of the Weddell (sp) Sea. This type of cruise is more expedition.. so if something fancies the expedition director or the ship's captain, we do it. There's no forced ports of call.
The crew is wonderful, the food is great... we are in the Antarctic itself for six days before we return to Ushuaia before flying home.
See ya.
david