Just read a lengthy piece talking about Discovery Services in LJ: Liverpool’s Discovery. It's a bit of a smackdown between Summon and EDS, with EDS being chosen by the U of Liverpool:
McCready was quick to make two caveats about the library’s decision to go with EDS. The decision, he says, isn’t about one product being better than another so much as it’s “about what is right for your situation. You need to look at your user community, your collection, and your mission. Every institution needs to come to its own decision.”
(thanks for the link, Helen)