I can't say that the vikings viewed left-handedness as positive, but they did not seem to put any kind of stigma on it. In at least two of the sagas, vikings described as very skilled switch to usding their left hands.

In the Færeyinga saga, Sigmundr boards Randvér's dragon longship with eleven men and cuts down many of Randvér's men before Randvér himself meets Sigmundr - they fight for a long time, and Sigmundr is unable to gain an advantage on Randvér beore he "showed his great skill" by throwing his sword into the air, shifting his shield to his right hand and catching his sword with his left hand. Thus able to attack Randvér from an unexpected (and undefended by his shield) side, he takes off Randvér's right leg below the knee and chops his head off when he falls.

Brennu-Njáls saga had the warrior Kari throw down his shield so hard that its edge is driven into the soil and it remains standing when Grani Gunnarsson throws a spear at him - then he catches the spear from the air with his left hand, turns it around and throws it back, still with his left hand and then picks up his shield (again with the left hand).

While absence of evidence is not evidence of absence, it seems like viking culture did not pace any special focus on using the "right" hand.

It is quite possible that both Kari and Sigmundr from the sagas above were left-handed, but used their weapons in the right hand since they fought together with others and the ability to use a pig's snout formation or a shield wall was dependent on every man having their shield in the same hand.