The main difference is that members cannot subscribe based on content type (in the new "digest" mode). Members can still choose to be notified instantly about all new posts, or about new comments/replies to posts they are following. Here's hwo the notification settings look when you switch to this mode:
Note: in my screenshot, the "All New Content" option is checked, but that is not checked by default. Members would have to opt into that option. However, "All New Content By Members You Follow" is checked by default.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .