The change in domains is to help us move away from being a simple comic site and allow us to become a community built around comics.  Interactions, in the past, have been limited to commenting on individual comic pages.

With the new site you can now Register for an account, participate in groups related to each comic and earn points usable towards rewards and eventually get badges for participating in the community.

Groups are intended to be a single focus point for community interaction related to a comic outside of commenting on an individual comic page.  The old commenting system still exists, to comment on a comic all you will need is an email address, just like on Petite Symphony. If you are logged in when you comment, you will also earn points for every comment or forum post that eventually can be used to get special members only rewards such as background images or avatars.

To help facilitate supporting our artists, you can also earn Patreon badges that will (eventually) display on your profile and your avatar.

Not all features are in place yet, as they are not crucial for the site launch, but should be available shortly.  Some of the new features currently active on the site:

Earn points for many tasks such as visiting daily, posting comments, responding in the group forums or creating a new topic.
Note: Spammers or people who abuse the system will lose more points than they will gain if a post is deleted.

You can now directly mention another user in any comment, status update or forum conversation using @, they will be notified that you mentioned them. The @ link will also point to their profile. You can not mention users that do not have an account, so normal commenters will not get notifications.

Have your own persistent profile that can contain links to your twitter, facebook, deviantart or furaffinity pages.

(soon)
You will be able to participate in different quests that will award badges that will be displayed on your profile. Quests could be anything from signing up for a new account, participating in the forums so many times or visiting the site on a specific day or week. This feature was not critical for launch so it is not quite ready yet.