Vulture.com have a relatively short interview up with Viggo Mortensen. The interview is mainly about his recent work, but he does go on to say that he watched The Hobbit in Argentina, and thought it was "fun".
Yeah, I did. I went on opening day to see it. I was actually in Argentina, and I went with a bunch of kids and their parents. It was kind of a party atmosphere, it was fun, it was in 3-D, and they had popcorn. I enjoyed it. In particular it was nice to see some of the landscapes I remembered. It was a nice trip down memory lane, where we’d shot near some of the places where I’d gone camping or fishing.