A detailed Information World Review article by the well-known Davey Winder, evaluating various academic search options from the point-of-view of a techie/journalist rather than a librarian. It’s a year old now, and seems to ignore the needs of the arts & humanities, but is still a useful everyman overview…
“One point often overlooked by many amateur researchers is that while the searching at IngentaConnect and Google Scholar may well be free, the hits generated often involve payment of some kind to access.”