We've been trying to get our SSO stuff up and working and it is now mostly working really well - the sign in link at the top of the forums page takes users to our sign in page and we can pass the SSO_TOKEN when directing to the forums to automatically log users in.
There are 2 remaining problems we are trying to figure out how to solve.
Firstly, if the user is not signed in when using the forums and creates a new post, they are directed to our login page (which is fine), but the return url querystring parameter is just the forum page and consequently when they return after login, they are not returned to the "new post" page and the post title they had typed is lost (i.e. they have start the new post process again).
Secondly (and more critically) the SSO login redirect doesn't appear to work for the feedback widget. When trying to create a new post directly from the feedback widget, the redirect happens to our login page is shown (but in a child frame), but when the login completes and the user is returned to the feedback widget (again with the original typed title lost) and tries to create a new post again the redirect to the login page happens again (i.e. the user gets stuck in a login loop).
Our objective is to allow users to a) automatically be signed in using the SSO_TOKEN if they happen to be signed in when we navigate to the forums from our site, b) provide the option for users that have already registered at our site to login using their existing credentials, c) ideally also allow them to login with your existing login options as an alternative to logging in at our site and SSO, d) have this work in a way that doesn't require them to retype details once they are logged in.
I wonder if you have considered allowing an embedded SSO login page, perhaps as an additional option to your existing sign in options, so that the redirect isn't necessary?