I agree whole heartedly that Samsung Social Hub sucks. Like you, having just updated to ICS on my Galaxy S2 I find that it is not possible to set up my PlusNet e-mail account simply because there is nowhere to enter a "Username" which is different from the "Email address" and is required to be entered to be able to log into the account. As a for instance the e-mail address is 'email@example.com' all I need to be able to log into the account is the 'username' portion. It is only because I took a backup of my Email account information before the update that I am able to access this account on ICS.
I had noticed before, on Gingerbread, that the setup of e-mail accounts was a little restrictive in the configuration options and I had hoped that things were going to improve on ICS, but this is a big step backwards as far as I am concerned.
Am I missing something? Are there some further hidden options anywhere? This is an obvious area for improvement me thinks.
---------- Post added at 11:39 PM ---------- Previous post was at 10:58 PM ----------
Ah ok, I take it all back. I have found the hidden settings. If you uncheck "Push notifications" then the "Microsoft Exchange ActiveSync" button changes to "Manual setup". Pressing this allows you to enter the elusive username that I was struggling with before.