Guam was surprisingly good, however we treated it as a joke, and had 0 expectations.
We had 3 nights there (originally only wanted 1). It is a country stuck in the 90's, you walk into the mall there and it is dead set what you would expect at an Australian suburban mall in 1995. During the day you have the beaches which are similar to the Caribbean with reefs etc. At night however, if you are in the tourist part there is nothing to do (we saw 2 movies over the 3 nights). The breakup of visitors is about 90% Japanese Families.
Also, if booking accommodation, check out some japanese links, many of the properties we saw were not even on expedia / agoda.
Vietnam during winter (this was my 4th trip, all others during summer) sucked. There was so much pollution that after a week it had a real impact on everyones health and mood.
The only upside is that there were a ton of tourists, so lots of people to meet and have a good time with.