I've noticed a few mentions[1] that RedLightGreen is modeled on Amazon as well as Google. I know this got started in our own information about the system, in which we stated RedLightGreen would be more like Amazon or Google than an OPAC. (Perhaps i should have read the document with a eye for smaller details than I did.) We investigated some features of Amazon that we would have been willing to include in the system -- specifically the reviews. While the Amazon reviews may be wonderful for selling books to the consumer or the self-directed reader, college students looking for books don't want to know what other college students think. They expressed distrust.
They would like the additional bookseller information -- the image of the book cover, the publisher's blurb, and professional reviews. Depending on the results of the RedLightGreen pilot study, those features may get pulled into the dataset.
Amazon makes acquiring the found item as easy as possible; we'd like to emulate that. I've been a little surprised at the cynicism and distrust of students, though -- the inclusion of bookseller links on the results page produced negative feedback. This doesn't make RedLightGreen unlike an OPAC, though. I suspect university librarians make as much use of the web interface to their systems to get library materials into the hands of their students as fast as possible. RedLightGreen's efficiency will depend a great deal on the local library's ability to put the item in the hands of the user.
I suspect that Amazon and OPACs have a strength more in common with each other than with the pilot version of RedLightGreen, and that is the speed with which a known item search can be completed. We've biased the RedLightGreen interface for the user who is not a specialist, who is looking for works about a topic, and who has their own language to describe that topic. In doing so, i suspect that searches for known but uncommon (few editions) works will be supported better by Amazon or an OPAC than RedLightGreen. On the other hand, if you know you're interested in the caste system in India, a wide net cast into Amazon is going to pull up to many titles not of interest.