The Vikings are very OK. I got them in my first game (after selecting "random leader"). I think the UB giving the extra ship movement is quite good, certainly with the amphibious Berserker, but it did not make a big difference to me in my game. I was on a continent of a standard map together with two other civs.
Navy in the early games doesn't really have a lot to do, in my opinion. I did not encounter barb galleys along the cost, and the AI was just exloring with his single trireme, so apart from my few (two to be exact) early exploring and defending triremes I did not really have to use these.
Jaca