Yes, "KC s2M+MC" plugin changes a lot. It have new features (for both Basic and Pro versions), new versions, and a new license...
First about new versions - there is 3 versions: Existing Basic version is turned to Free. You can see it at WP repository. Existing Pro version is the new Basic one! New Pro version have several new features:
Now when s2Member® changes the user's level, like when demotes the member account at EOT, Mailchimp® is updated too. Means, if you choose to synchronize "user role", it will be synchronized just after the change, and you will have the real role in MC's merge tag.
Additionally, the "Role" field now can be synchronized both by "system name" like "s2member_level1", or by your name you set in s2M's options like "Professional Member".
Now in "Users" page you will have a new column "Lists", where will be shown each list where the user is subscribed. Well, if you not need it, just hide it by "Screen options" there.
Can not sort users by this new column. But can filter them! There is two new links for each list, just under the system filters links: "in ListX" and "NOT in ListX". Means "all members in ListX" (where "ListX" is the list ID) and "all members NOT in ListX". It was an epic battle with WP and s2M to build them, hope they will do your life easier.
Moreover, you can check if a member is in some list by s2M conditionals like:
content available for the user who is subscribed to the ListX
content available for the user who is NOT subscribed to the ListX
But biggest update is that now plugin allows you to synchronize each ccap separately with a merge tag. And it's bi-directional! Means, this allows you to create a field in MC form and the plugin will set a ccap to member for you, automatically! Sure, you will get the merge updated if you delete the ccap from Admin area too. Or if member buy some ccap too. And so on, open your mind, there waits lot of useful possibilities!
Note that such massive changes have some "bad sides"... You have to click "Check synchronization" button often. For example, sometimes people can be shown as "subscribed" in "Users" page, while they are not. So before you do some change of a member, related to lists, check synchronization first.
Out of the new features, there is lot of improvements, like speeding up the communications between WP and MC, bug fixings etc. It's good to update it just because of these...
License changes too. Upgrading from Basic to Pro is as usual. Upgrading from "Basic old" to "Basic new" and from "Pro old" to "Pro new" will be paid too. You will have need buttons there on the page, and a download link(s), as usual.
if you choose to move to a new version, do not deactivate the plugin, just save new files above existing ones. This way you will save all your settings.
After installing the new Pro version, please click "Check synchronization" button - there is some changes in database, what must be done. Again, click it every time after you synchronize manually, just in case.
That's all today, hope new features will help you in your everyday jobs.