The services has the tagline “Stand on the shoulders of giants.” It includes a cross referenced citation link for each paper, which is very cool, and as we all know, the basis of PageRank (and the WWW) in the first place. Here’s a search for vertical or domain specific search, for example.
This move marks a trend toward making usually invisible (and useful) information more accessible, one that I could imagine spreads to other domains, perhaps ones more commercial in nature. (Scholar does not have ads in it, at least for now). The special ranking algorithm and policies for dealing with the nature of a structured document universe such as this clearly scales to other opportunities – ie, travel, automotive, business information and the like.
Here’s Resourceshelf’s take on this, and SEW’s.