Worth a look around at the famous (infamous?) sites of the Peronist era and especially for the Tango!! Not a city I would rush to visit again, after a total of four days there but then the unusually extreme tempertures restricted our activities so maybe, with a little more walking, we might have seen more but even so, not my recommendation to cruisers although worth a day or so to experience that erotic tango!
Interesting architecture and a good place to begin tours - the Beagle Channel and the Glacier (although we have to rely on the comments of others for that one). Very good for bird watchers and supposedly, the southernmost city in the world so perhaps worth a vivist for that alone. Other than by cruise ship, the quickest way is by air from Buenos Aires - four hours, its a long country, Argentina!