Saw the road map and last RC2 and still not viewing that trully strategical AND essentiel function for un blog network : registration on several blogs for already network registered users !!!!
For the moment it is NOT POSSIBLE and there is NO plugin around allowing a "role request on this site" mentionning "you are already member of X sites on this network would you mind adding this one", as the groups integration on facebook this is the same. Just imagine that need a separate email or nickname to register on a group on FB or any other blog plateform !
Found a plugin restablishing the per site registration process, but once registered, no other site is possible :(
This is essential and trully dont understand how this feature is not in the WP multisite core ! A blog network that does not allow users to register on several blogs is just incredible !
Hopping that will be taken in consideration....