While I am one of those that would hand over my saved stories, I wonder about the validity of any conclusions you would draw from the group analysis due to the dual nature of the save button. The same button that is used to up vote an article is also the same button that HNers use to save an article to read later, but might not upvote the article after having read it. I'm not quite sure what could be concluded from such an unclean data point.
That's my point, there is no way to save a story without upvoting it, but the two are mutually exclusive, or atleast should be. People will use the vote button as a way to bookmark stories that they want to read later but are forced to vote as well.
Judging from the comments in this post, I don't think many people knew about the saved stories feature to begin with, and if they do I doubt many upvote a story purely to read it later. There are better services to do that like Instapaper.
If I might add a data point, When I am busy, I primarily use the upvote button to read later. It's my instapaper.
I upvote the article based on the content when I am not too busy.
