On point about build quality here. People hate on Samsung's plastic but you know what, as ugly as it is it is very durable. You look through the 920 forums and it is littered with issues. Just like any bits of tech, people get lemons.
Someone posted a list of the current apps in the Nokia collection. OP, if you need many of those, then Nokia is the way to go. Otherwise, at the price point you've mentioned, the Ativ S gives better bang for buck. Remember, you cannot change 8GB (technical about 7.44GB) of internal storage...that's what you get on the 820.