Evernote, with its elephant logo (geddit?) is essentially a brain dump database that stores URLs, text and images. To be honest, my first impression is "Meh", although there is one very useful feature - text recognition in images, which is very useful, and in truth, probably the only reason I'll continue to use Evernote - take a snap with your phone, upload and it's available as text. Access to Evernote comes via a downloadable desktop application (but there's no Linux version), or a browser bookmarklet, which only offers limited functionality.
The nearest thing I can think of to compare Evernote to is Zotero, which is more limited in scope, essentially just a reference manager, but slicker and better at what it does. Zotero definitely offers more than Evernote in terms of the advantages of social bookmarking services. Unfortunately, Zotero is tightly linked to the Fireox/Flock browers only and will not work with Internet Explorer. Although UoL students have access to Firefox on the University system, it's not easy to get at and it would be difficult if not impossible to "force" them to use it (although I'm all in favour of gentle encouragement).
Both services are free at present but "Evernote Premium" will cost something at some point in future. On balance, I can't recommend either service to our students - they'll be better off with a core service such as del.icio.us, Google Docs or other alternatives.