Currently I'm working outside the university network (you'd hope within a university network with relevant IP addresses anyone would be able to figure out how to organise access management) but under the new system instead of being able to sign in to Athens once and then access all journal articles via links in commonly used search engines like pubmed, or via links in journal articles, now I have to search the university database of subscribed journals, then enter the citation, then wait while it chugs along at about one mile per hour to finally serve up the paper. If I'm lucky the journal may have got around to adding the 'UK Access Management Federation' to its long list of alternative logins, and then if I find it, and select the relevant UK university from the long list, I may be able to get it to recognise that I've already signed in (saving me the time to type in my login and password, but little else).
So why change? Apparently 'federated access management' (where they ask your institution if you're signed in there, rather than having you sign in directly) is the bees knees, according to JISC:
Librarians will be free of the burden of user name and password administration, and will have new tools for managing licenses and service subscriptions.
IT managers will have more control of the access management process through enhancements to enterprise directories, although this will require additional institutional effort in the short term.
Institutions will have a single service to meet the requirements of e-learning, e-research and library-managed resources. Simplification of the authentication process has also proven to lead to increased use of subscribed services."